If you're so smart, why are you dead?
I've gotten some good answers that I'm still thinking over, of which many seem to be along the lines of "We're doing better, but not nearly as much better as you would expect from our greater technology and economy, which suggests what better science giveth, worse politics taketh away."
One particular argument I heard, which I found fascinating, was this: classical Athens had a population of about 150,000 people. The modern Anglosphere has a population of about 450,000,000 people, ie about three thousand times that of classical Athens.
But classical Athens gave us, all within a single human lifespan, Aristotle, Plato, and Socrates. Within a single lifespan it gave us Sophocles, Aeschylus, and Euripides. So if modern society were just as good as classical Athens, we should be producing a thousand Platos and Sophocleses a generation.
It would be a matter of opinion whether our greatest living philosopher and author are up to Athenian standards (for comparison: a quick Google search suggests Saul Kripke as a consensus candidate for greatest living philosopher and Cormac McCarthy as greatest living author). But it seems pretty clear, at least to my friend, that we don't have a thousand Platos and Sophocleses (actually, his analogy was a thousand Shakespeares, which is less phonetically awkward than Sophocleses, so let's stick with that).
So his argument is that since Plato/Shakespeare rates are only a thousandth what they were in Athens, modern society must be doing something very wrong, either in poor education, stifling creativity/forcing conformity, or having terrible institutions for patronizing the arts and sciences. Even if "classical Athens" or "Elizabethan England" are too high standards, one would at least expect us to do better than a tenth of one percent of the genius rate.
And I had a few thoughts on that.
1. Low-hanging fruit effect. I think most of the mathematicians I know, if asked, could invent a proof of the Pythagorean Theorem they'd never heard before (although no doubt it would have been discovered somewhere by someone). I wouldn't be surprised if there were a million people in the Anglosphere who could do this. On the other hand, there was only one guy who could prove Fermat's Last Theorem, and even he had trouble.
But Pythagoras was justly hailed as one of the great ancient mathematicians for his discovery. Granted, coming up with the idea of the theorem in 500 BC is harder than proving it when you already know what you're looking for and have all of modern mathematics at your disposal, so give him credit for that. Still, if someone asks "Where are all our Pythagorases?" it seems reasonable to point to all of the people who can do what Pythagoras did but receive no recognition for it, at the same time as we're recognizing people who solve vastly harder problems.
2. Ancients weren't really that great.
Back when I was first getting into atheism I remember hearing a lot of people say "Sure, the Bible is brilliant literature and contains amazing moral teachings, it's just not factually accurate." And then many years later for the first time I heard someone assert "The Bible's actually not that great, as literature goes. We just hear it so often that it gets worked into our head as a paradigm example of how literature should be, and then judge it as brilliant because it fits the paradigm so nicely." And although we are impressed by Biblical turns of phrase like "the blind leading the blind" and "let there be light", some of them were just common ancient proverbs that happened to be captured in the Bible, and others, when you think about them as just normal turns of phrase and not as the deep archetypes that they've become, are just kind of normal. What finally convinced me of this was hearing Muslims rave about the literary brilliance of the Koran - I've tried to read the Koran, and it's one of the worst-written, most uninspiring books I've ever seen (yes, I know people say it loses a lot in translation. But the Bible's also translated.)
There was an interesting experiment I can't find right now where they separated teenagers out into artificial communities and gave them various media of the sort teenagers like - let's say albums by different bands. After enough time, some albums had become popular in each community - had attained "classic" status - while others languished forgotten. But the "classic" albums were different in each community - it had less to do with any real quality and more to do with chance as popular people spread them and they became loved precisely for their familiarity.
If you gave me a play by Shakespeare, and a play by let's say the fifth best playwright of Shakespeare's age, and I'd never heard of either and I didn't know enough Shakespeare to be able to see his "signature" in works and guess it was him, it doesn't seem obvious to me that I would rate the Shakespeare play as vastly better. If I read through the "to be or not to be" soliloquy in Hamlet without knowing it was supposed to be the greatest passage in English literature, I'm not even sure I would stop reading long enough to think "Wow, this is an abnormally good soliloquy here".
And don't get me started on Plato. The man basically made the most basic philosophical mistake possible - just going around, reifying everything. It's like the Platonic archetype of philosophical mistakes. His political theory was "What if we just give philosophers control of everything, that'll work out, right?" It may be that in ancient times, with their lack of exploration in philosophyspace, even discovering such interesting mistakes like these is an accomplishment. But I don't know if they rate making him the greatest philosophical genius of all time. That's just an effect of him being Old And Therefore Venerable. If you're making a movie, and you need to show one of the characters is Very Sophisticated, you have them reading a book of Plato's Dialogues and everyone goes "Oh, that character is very Sophisticated. Got it."
3. Limited demand. Literature scales really well. If there's a civilization of a million people, then one great author can have her book read by all one million people. If there's a civilization of a billion people, then one great author can have her book read by all one billion people. If people read a constant number of books per year by different authors (let's say five), and each author puts out a book per year, we only need the same amount of authors to satisfy a tiny population as we do to satisfy a large population. Therefore, we would expect a smaller proportion of the large population to be authors - five out of a billion vs. five out of a million.
In practice that's not exactly what happens. Everyone has different tastes, so even if one book is "best" it might not be best for everyone. We can get slightly more authors by having them pander to different tastes and genres, still more authors by taking advantage of random noise (in reality, not everyone is going to buy the one "best" book, because some people just won't know about it and will buy one with a shinier cover) and so on. But in general we would expect proportionally fewer authors, and much fewer famous authors in the modern 450 million person Anglosphere than in 150,000 person Athens.
If we actually had a thousand Shakespeares, that wouldn't change the fact that there's a market for maybe a dozen new big Broadway shows per year. It would just mean 988 of those Shakespeares would have to languish in unpaid internships and eventually quit and give up and work at Starbucks while a mostly randomly selected twelve of them make it big.
Likewise, as the philosophy community gets bigger, it will have to do some combination of either faction into subdisciplines or just talk about a handful of the most famous philosophers. In the first option none of those philosophers will ever gain the status of Plato ("Ooh, you addressed some problems of ontology within a Continental meta-anarchist framework, big deal") and in the latter once again only a few people will ever get fame.
4. Perceived arrogance. I thought of becoming a philosophy grad student, once. If I had, I would have kept my head low for several years, found a subsubspecialty, and written journal articles about it. I probably wouldn't have tried to completely reinvent our picture of the world, because then people would have laughed at me. It would be like "Who do you think you are, Plato or somebody?" People who try to completely reinvent our picture of the world never get tenure, which is why all the really creative work I've seen lately has been on blogs.
But if you're Plato, you don't have to worry about that. No one had even tried to come up with anything as ambitious as his theory in his own time. If someone had asked "Who do you think you are, Plato or somebody?" he could have just said "Yes, I'm Plato" and everyone else would have been like "Oh, right."
I don't know whether all of these things are defenses of modernity rather than perhaps the very critiques of modernity that a reactionary might dislike. For example, there are so many people in fields like philosophy that realistically to have any chance of making a name for yourself you have to subspecialize in a much smaller field. This makes logical sense, but it also means that status competitions prevent anyone from being a generalist to the same degree Plato was.
And status competitions in fields with too many people also tempt people to come up with flashy (rather than good) ideas. I think a reactionary would complain that you couldn't just be Sophocles and write an awesome tragedy about a Greek myth today. You'd have to set it in 1940s Brooklyn, and the whole play would have to be performed in the dark, and it would all have to be a metaphor for colonialism somehow. And it is true that in a world with so many playwrights competing against each other, it's more important to stand out, and what people do to standout today becomes a prerequisite of not looking stodgy and conservative tomorrow, and eventually things get ridiculous. But I don't think our political institutions, or anything about modern society is to blame for that. That's just what happens when you have too many wannabe playwrights in a society.
But I still don't think the original point is correct. The reason we don't see a thousand obviously Plato-caliber intellects running around is a combination of low-hanging fruit and the fact that we judge people by fame. That leads us to overestimate Plato, who was a big fish in a small pond, and underestimate moderns who don't get famous simply because there aren't enough easy big problems or enough fame to go around.
"If you're so smart, why are you dead?" may be silly, but "if you're so smart, why aren't you famous" might be more dangerous.