One of the things that we can't necessarily know is whether Terry Pratchett was likely to become Terry Pratchett, given his beginning. We never do hear about the failures. It's not just that mediocre students often fail to make something of themselves- how often do mediocre students with a mind like Pratchett's accomplish world changing things like Discworld? If you knew a priori that you had such a mind, and wanted to maximize your contributions, would it be a good idea to be an aimless student?
That said, it may be that you wouldn't be likely to get a Pratchett without a certain baseline of failed attempts; and that a youth spent in such a way may be bad for the individual on average and good for society in aggregate. It would be an interesting dilemma.
As far as I can tell, LW-style rationality appears to be heavily based on the "outside view", i.e. the view that you would take if you knew the outcomes of past endeavors similar to the one you're looking at, but not the specific details. By definition, the outside view gives the most probable outcome, but when specific details start to overwhelm generalities, it can fail quite spectacularly. Pratchett was not at all a member of a representative sample; indeed from what I've read of him he seemed quite exceptional. So it's reasonable to say that although "work on being a better student and looking for ways to make more money early on" might have been good advice for a normal student, it wouldn't have been such good advice for Pratchett. The existence of a few extraordinary counterexamples doesn't obviate the fact that the advice still works for a majority of ordinary people.
There's some evidence that in many respects LW people are also not normal or ordinary people, statistically speaking. (Though of course not generally as remarkable -- in outcome, at least -- as Pratchett.)
I read a tremendous amount of Overcoming Bias/The Sequences/Less Wrong from ages ~18-21 as I was transitioning from high school and into college. I cannot overstate how much this exposure impacted my mindset during these - generally tumultuous - years.
I don't recall ever feeling that I should be ~doing something more~ or doing anything other than exploring the world around me as I decided what I wanted to do with my life.
While a lot of the drive behind Less Wrong has evolved to emphasize optimal investment/philanthropy/career choices/etc, I don't think the underlying ideas and motivations behind "LW-style rationality" would condemn anyone for pursuing and exploring what they were interested in, regardless of level of salary or status associated with what they loved.
If someone came to lesswrong and asked: "I'm an average student, I don't know what to do with my life. What should I do?" Then I would probably recommend studying hard, getting a good job, and trying to figure out what they enjoyed/were good at so they could specialize. Good general advice if I don't know about the person.
On the other hand, if Young Pratchett had asked the question: "I'm a bad student, but I love writing and I'm obsessed with the news. What should I do?" I would probably recommend concentrating on his writing classes and getting a job that involved the news and writing, like the newspaper job he got. Advice tailored to the person.
You don't win by competing with people who are better than you at something you are bad at. You win by finding what is important to you, what you enjoy, and what you are best at and doing that as well as you can. Giving the same advice to everyone seems like the way to lose at giving good advice.
Seems to me that study well and get a good job is exactly the same as don't study bad and don't get a bad job, and don't stop studying and working, which is easy to say and easy to interpret; while be unique has some 'emergent properties'. Now... setting the clock for five minutes...
Encouraging someone to be agenty can be effectively done by putting them in charge of communal efforts. It's not enough to bear some (heroic) responsibility yourself, you have to learn to nurture the tiniest sprouts of initiative of people around you. Even if they want to work in a newspaper.
Among other things, it teaches you to 1) never drop the ball, 2) recognize the vaguest idea as one that has potential - or doesn't, but as the main thing is 1), you will stick your neck out and go with it. Even if it sounds irrational. And when it fails, you must - because there's nobody else to do it, because if you lose a person, nobody's coming in their place - say, we shall try it a different way. Then comes a session of 'really hard thinking', then you give up, then they call you and say something like, of course, this is what I did wrong...
And that doesn't mean you can become great at something, just that you'll keep trying to.
For every A+ list actor making millions per film there's tens of thousands of starving wannabes trying to get a break working for half nothing.
For every footballer making 100K per game there's tens of thousands of teens trying to break in making nothing.
For every A list author there's a hundred thousand people pouring their heart and soul into a book that few will ever read.
Pratchett was an exceptional human being.
He was 1 in a million.
But there's 7000 people who are one in a million and only 10 of them get to be in the top 10 best selling authors of the decade.
Making your choices based on the expected return of an investment isn't proven to be a bad idea by pointing to people who've made tens of millions from the lottery.
Pratchett was exceptional but there's a good chance that if at the start a few reviewers had been more negative, if he'd been feeling a bit off while writing some pieces that the discworld may never have become what it did.
He was 1 in a million.
But there's 7000 people who are one in a million and only 10 of them get to be in the top 10 best selling authors of the decade.
But everyone knows one in a million chances almost always work!
I feel that part of the problem is that, on average, "try to be a better student and find a well-paying job early on" is good advice. One of the main things I'd like to tell past!me is that I should develop better study habits and go into IT whatever anyone else said. I can't say with absolute certainty it would have made my life better/easier but it probably would have.
For some people (and I won't guess about the proportion of this group relative to the population), "study hard and find a well-paying job" isn't the optimal advice. For Terry Prachett it clearly wasn't and for Eliezer Yudkowsky it wasn't either.
I guess it's really about your competitive advantage, finding your niche and your potential but all of those are hard to discover (and often harder to discover from the inside). I don't think a solution is to stop telling people to study and find a good job, but part of a solution might be to give (young) people more ways of discovering their own potential (preferably at school?). There's a good chance Pratchett's creative writing exercises were noticeably better than those of his peers and from what I read it was clear from an early age that Yudkowsky's advantage didn't lie in strictly academic successes.
Pratchett's lecture at Trinity
For a long time, I've been dubious about "rationality is winning". While it protects against one dangerous line of thought (I was right! It's just that the universe didn't cooperate), it fails to mention a time scale-- sometimes you lose before you win. And sometimes you wander around for a while with no apparent purpose, and then you find something unlikely and valuable.
Pratchett's lecture includes a description of his early life, and I don't think any rational person or any rational parent would have seen his early life as any sort of sensible goal-seeking, or likely to lead to winning in any sense.
Pratchett was a fairly bad student, though he did better when he had less competition. He read all the bound volumes of Punch (the major British satirical magazine), and learned from that classic.
He became a reporter for a local newspaper, a job with modest status and low salary. (In one of his novels, he mentions the voracious appetite of a newspaper-- it's got to have news every day. Somehow, this seemed more intensely true than the large number of other sensible things he said in his books. Looks like I was on to something.)
It seems to me that LW-style rationality would have had him working on being a better student and looking for ways to make more money early on, and he probably wouldn't have written Discworld.
On the other hand, Eliezer is doing quite well, and on yet another and possibly gripping hand, I doubt that going for increasing the probability of success would have started with "think really hard about existential risks".