Sounds like you're depressed.

I'm curious if others have similar experiences or clarifying thoughts.

I have a similar experience. I'm not sure what to write, but here are some thoughts.

• The healthy kid probably wouldn't be excited by a back-flip robot arbitrarily instantiated in a hell. Its awesomeness is context-dependent.
• What kinds of motivation do you have access to?
  • In fiction, the protagonists have motivation even when the world seems really bad. They want to change it. Most real humans instead keep the torture out of mind, but not you.
  • Separately, a theorist may devote so much energy to their object of study that it becomes intrinsically important to their mind. This is myopic in a way (it's about the thing itself). But maybe it can be non-myopic if thinking about it is instrumental, so contextualizing doesn't diminish it. Maybe passion and heroic motivation can then fuse together.

I think the basic mechanism here is that people actually judge most things by their pleasantness to a much larger degree than they tend to admit, and general bad mood decreases pleasantness.

Directionally I agree with lc saying it sounds like you're depressed, but I don't think it actually has to be anywhere near clinical depression. I think "I'm generally sadder so things seem less exciting" is a very commonly true description. You reporting it could have more to do with you being more introspective than with how extreme the condition is.

The general remedy is just to improve your well-being, which of course is very difficult. But I don't think there's any conceptual move you can make that will help here; the core issue very much seems to be a lack of fulfillment.

It makes sense that getting negative information about the world would reduce motivation for a while. But I'm not sure that "a healthy kid would be excited about making a robot that could serve coffee and do a backflip" is necessarily true. The judgment about what is "healthy" vs not is doing a lot of work there, and deserves to be questioned. Suppose you were a kid in a war zone - a "healthy" response in that situation is different from a "healthy" response in a safe suburban first-world neighborhood, which is different from a "healthy" response in a future utopia where many problems that exist today have been solved. Maybe in future we'll get to a world that is so good, the most exciting thing isn't something like "maybe we can end world hunger" or "we could reengineer the food system to mean it doesn't cause any suffering to animals" or "we could turn the natural world into a garden where many of the wild animal suffering issues that currently exist don't any more" or "maybe we can cure cancer permanently and make dying of 'old age' a thing that just doesn't happen any more" but "someone invented an exciting new flavour of cheese that nobody has ever tasted before". We might shrug and go "why does that matter very much?" while the people of that future world could consider not being excited about the new cheese a sign of a problem with motivation. Similarly, someone in a war zone may consider most things people who are not in war zones occupy themselves with fairly trivial and unmotivating, and have a startle response and level of vigilance to threat that would be very dysfunctional in a quiet suburb, and all that makes good sense to me.

With that as background, what you're saying is, you're finding the actual world is a worse place than you expected. EDIT TO ADD: And that is shifting what feels important and motivating to you, such that things that might once have seemed important, and might seem important to the people around you, might seem relatively less important now. And the question becomes, how to respond to that in a healthy way. Where what I mean by "healthy" is something like "you can continue to function, have a life that is at least worth living from your own perspective, and all else equal you having a better life is good and you shouldn't lose sight of that, and as a healthy functioning person, you should be able to find the motivation to try to do things about the problems you see in the world".

If seeing certain things is both giving you a much worse life and also compromising your ability to do things in the world, then it's worth questioning whether that's good. It is not common here on LessWrong to encourage looking away from things that are true, but there is the concept of an infohazard, a thing that it is bad to spread knowledge of. And I personally would endorse looking away from something you don't know how to deal with, temporarily, until you can find a way that it won't compromise your ability to function.

Here's my personal perspective: Yep, there are horrible things about the world. I saw this early, and when I for example learned about the holocaust as a thing that happened, around age 10, I was like "yep, that seems like the sort of thing humans would do sometimes, I'm actually surprised people are treating this as a singularly bad event?" rather than being surprised by how bad it was. But as I've grown, I've also come to understand that my original thought that this is just the way the world is, had basically always been, and likely would always be, because basically nobody cared enough to try and change it, was wrong. Over time, the world has changed due to human action, and the things that are bad about it now can likewise be changed. My grandparents lived in a world that was more horrible than that of my parents, and a lot of the problems I saw with the people around me, were sort of things that happened because they grew up in the equivalent of a war zone - except that people at the time didn't think of it as a traumatic environment, they just thought of it as normal. A lot of the problems that existed for me as a kid, people have taken action about, and the children of today have their own struggles, but the environment in which they are growing is kinder and better for a person's healthy growth and development. On average - there are pockets where things have stayed the same or gotten worse, and the status quo is still very bad, don't think I have whatever colour of glasses on that would result in thinking everything is OK, but less bad, and that is an important improvement.

Now, the focus of your "the world is horrible" thoughts seems to be around the suffering of sentient beings, not particularly focused on humans as my thoughts were in childhood. So here are some thoughts about that. Another change that has happened for me over time is, I used to think that the adults in the room knew basically all there was to know, and had learned all that was learnable - for the first decade or so of my life, whenever I had a question, someone almost always had an answer, so I formed the impression that most questions had already been answered, that our society was old and wise and stable. I now think the opposite. Our society is a flailing infant, or a system less coordinated than that with no society-level self-awareness, or maybe at best a confused adolescent who's undergone some abuse. When it comes to the suffering of human beings, it's relatively recent, within the lifetimes of those currently alive, when the accepted wisdom was that nonverbal infants couldn't feel pain and so there was no reason to provide anesthetic when doing surgeries on them. And that's human infants, the things our fledgling moral systems are supposedly most concerned about protecting the welfare of. Supposedly torturing infants would be close to the worst thing, except somehow we mistakenly decided that below a certain age that was not a possible thing to do, and that position persisted for decades. That is how bad we are at figuring out basic things about the world. I've been following the research on the cognition and experience of nonhuman animals, and the pattern I see repeating in most cases is "these are more human-like than we assumed, their experience is more like ours than we thought, they can do the things we thought made us special and more important". 80,000 hours (podcast) has had a couple good episodes, on insect and fish welfare, recently. In the case of insect welfare, the researcher they interviewed assumed at first, when she was doing experiments on insects that didn't have the same ethics forms to fill out as experiments on mammals, that someone had checked and confirmed that those concerns didn't apply to insects. But it turned out, nobody had checked, it was just assumed that insects lacked morally-relevant capacities, and so she ended up doing the checking. And for fish, most of the research on their cognition and perception and sentience etc. has been done in the past decade, and we are still finding out really basic things about various species (fish are a broad category of thing, and the impression is that for any capacity, the answer to the question "can fish do this?" is "almost always at least some fish can, but we've only researched a small portion of the many thousands of species that exist".)

So: Yes, the world is horrible in many ways. Humanity is just barely pulling itself up out of the muck, and although the present is bad, the past was in many ways worse. Things are typically much better now in areas where people have looked at the horrors and tried to end them. There are still many places we haven't looked. And our power as a species is growing - in my grandparents' time, trying to end wild animal suffering would have seemed literally insane. Right now it seems like  a really heavy lift, something that might be possible but we don't have even the basic building blocks of how to do it in place, let alone a plan that we could be confident enough that it would work where we could get the world's politicians on-side. But a few people are talking about it, at least. Maybe if we survive long enough, turning the world into a suffering-free garden will seem like an obvious and easy thing to do. And to me, being alive at this time, when there are horrors to be ended but we potentially have the power to actually do it, for the first time ever, is exciting. There is much work to do, and people around the world are starting to do it. So, a robot that can do a backflip? Not so exciting. The fact that systems have been put in place very recently (since around 2010) which mean I have the power to save or massively improve thousands of lives over the course of my career through effective donations, because we haven't yet solved what are (now) easy-ish problems to solve? Exciting! The fact that new problems are getting the spotlight, new horrors brought into view, which were happening but of which I was unaware as a child? Also... kind of exciting? I mean, it's bad that they were happening, but good for us to know. Because I believe that once we see something that should change, we can and will change it. Likely over decades rather than centuries. And I get to be a part of that. So do you.

Could it be due to aliefs about attainability of success becoming lower, and that leading to lower motivation? (Cf. "motivation equation".) (It's less likely we'll be able to attain a flourishing post-human future if the world is deeply insane, mostly run by sociopaths, or similarly horrible.)

Or maybe: As one learns about horrors, the only thing that feels worth working on is mitigating the horrors; but that endeavour is difficult, has sparse (or zero) rewards, low probability of success, etc., and consequently does not feel very exciting?

(Also: IIUC, you keep updating towards "world is more horrible than I thought"? If so: why not update all the way, to the point that you can no longer predict which way you'll update in future?)