I don't think there is anything particularly scientific about transhumanism relative to other ideologies. They use science to achieve their goals, much like Catholics use science to prove that fetuses have heart beats or whatever. 

Really, this debate feels like it boils down to an individualistic vs collectivistic sense of self. In the collectivist view, dying is not that big of a deal. You can see this in action, when dying for your family, country, etc is seen as noble and great. Whereas an individual sacrificing their family to preserve themselves is less lauded (except in Individualist propaganda, where we're scolded for "judging" and supposed to "understand" the individual circumstances and so on).

I mean, you yourself say it, we have no idea what consciousness even is. Or if it's valuable at all. We're just going on a bunch of arbitrary intuitions here. Well, that's a bad standard. And it's not like we're running out of people, we can just create them as needed, indefinitely. So given that

1. we have a lot of humans, they aren't a particularly limited resource, and
2. few if any of the people have super unique, amazing perspectives, such that we really need to preserve that one person for extra time

Why not focus our energy on figuring out what we are, and decide the best course of action from there? 

It's only cruel if you've been brainwashed into thinking your life matters. If you never thought that, it's just normal. Accept your place and die so that our descendants (who we should work really hard to help so they turn out better than we are, and thus deserving of immortality should we ever actually attain it).

But then, if we've figured out how to make such amazing people, why not let there be lots of different ones, so they can flourish across many generations, instead of having just one generation forever? I mean, there isn't even that much to do. Well, there probably is, I'm just too basic to understand it because of my limited natural brain.

I guess transhumanism overall is really cool, taken as a whole package. It's just the life-extension part I find silly, especially if it's a priority rather than an afterthought. But even if you want transhumanism, aren't we far enough from it that the best path towards it is just raising better (smarter, more cooperative, etc) children? Seems like the biggest hindrance to scientific progress is just the state of the quality of human beings.

>Either too deep or I'm too dumb, didn't quite get it. Please explain less poetically.

Poorly worded on my part. I just mean that it's thanks to death that we get progress. The old die, and with them out of the way, the young can progress. Lots of fresh new perspectives are a feature of death.