Lucky is the fatal flaw in OK Computer. Mediocre and generic song in every way, unworthy of its company, and its effect on the tracklist is terrible as far as pacing.
But OKC has many other small flaws. Trying too hard in general is one of them. It oh so desperately wants to be this big ass statement on modern life- a flaw OKC shares with U2's Zooropa (1993) and Blur's Britpop trilogy, particularly the final installment The Great Escape (1995). These are poorly regarded albums in comparison, to which the acclaimed OKC is rarely compared, but they are actually the best, most underrated work of those (often overrated) artists, and both of those predecessors have many similarities to OKC, both in their satirical lyrics and their musical styles. They're also more deeply flawed (if arguably also more interesting), due to their prioritization of social commentary over listenability.
Fitter Happier is the one moment Radiohead almost leans in that direction. Musically, it's fine. But Fitter Happier is indicative of that trying. I don't think the album should lose that commentary, but it could've been more thoughtful and less cliche and on-the-nose. It makes Billy Corgan or Maynard James Keenan or Trent Reznor seem subtle. There are some good lyrics in that piece, but it happens to end with a really... shitty one. It could've been chopped in half and made its point. The point is already implied by most of the other songs anyway. The only reason to spell it out would be to prevent, say, far right readings of the album, but it didn't prevent that anyway, so you might as well leave it up to interpretation. "Such a pretty house and such a pretty garden," "we hope your rules and wisdom choke you," "I live in a town where you can't smell a thing.." these are far better expressions of the idea.
OK Computer is, as Radiohead themselves have said, a couple of songs too long, and very far from a masterpiece. But it's not that bad of an album. I have no idea why Pitchfork decided to celebrate it's birthday several months early tho.