Eegads. How do you even imagine what those people will be like?

Well, if, e.g. you're working on a special case of an unsolved problem using an ad hoc method with applicability that's clearly limited to that case, and you think that the problem will probably be solved in full generality with a more illuminating solution within the next 50 years, then you have good reason to believe that work along these lines has no lasting significance.

Sure, I don't think anyone I know really thinks of their work that way.

Not consciously, but there's a difference between doing research that you think could contribute substantially to human knowledge and research that you know won't. I think that a lot of mathematicians' work falls into the latter category.

This is a long conversation, but I think that there's a major issue of the publish or perish system (together with social pressures to be respectful to one's colleagues) leading to doublethink, where on an explicit level, people think that their own research and the research of their colleagues is interesting, because they're trying to make the best of the situation, but where there's a large element of belief-in-belief, and that they don't actually enjoy doing their work or hearing about their colleagues' work in seminars. Even when people do enjoy their work, they often don't know what they're missing out on by not working on things that they find most interesting on an emotional level.

The people two or three levels above me, though, they're putting out genuinely new stuff on the order of once every three to five years. Maybe not "the best mathematicians 50 years from now think this is amazing" stuff, but I think the tools will still be in use in the generation after mine. Similar to the way most of my toolbox was invented in the 70's-80's.

This sounds roughly similar to what I myself believe – the differences may be semantic. I think that work can be valuable even if people don't find it amazing. I also think that there are people outside of the top 200 mathematicians who do really interesting work of lasting historical value – just that it doesn't happen very often. (Weil said that you can tell that somebody is a really good mathematician if he or she has made two really good discoveries, and that Mordell is a counterexample.) It's also possible that I'd consider the people who you have in mind to be in the top 200 mathematicians even if they aren't considered to be so broadly.

I don't understand your concept of originality. It has to be created in a vacuum to be original?

It's hard to convey effect sizes in words. The standard that I have in mind is "producing knowledge that significantly changes experts' Bayesian priors" (whether it be about what mathematical facts are true, or which methods are useful in a given context, or what the best perspective on a given topic is). By "significantly changes" I mean something like "uncovers something that some experts would find surprising."

In the counterfactual where Vojta doesn't exist, does Mazur go on to write similar papers? Is that the problem?

I don't have enough subject matter knowledge to know how much Vojta added beyond what Mazur suggested (it could that upon learning more I would consider his marginal contributions to be really huge). I guess in bringing up those examples I didn't so much mean "Vojta and Wiles didn't do original work – it had already essentially been done by Mazur" as much as "the original contributions in math are more densely concentrated in a smaller number of people than one would guess from the outside," which in turn bears on the question of how someone should assess his or her prospects for doing genuinely original work in a given field.