Oakmont is an interesting case for me. In contrast to, say, Cypress Point or Shinnecock, which truly feel like someone's magnum opus where everything is firing on all cylinders, there's a whiff of amateur-ism in it? By no means is that a bad thing (in fact I'd say it produces some of the most captivating moments). But there's a variety of bunker styles (church pews, grass down, small, pot bunker-esque vs massive sandy areas), the greens uniquely lack cohesion (but are full of interest) and they're big and spacious on-grade like the 8th or the 7th with its perched back pad a la Donald Ross, and the routing is somewhat rudimentary in contrast to something else in the top 10-20 in the US. To me, it really feels like an amateur throwing a bunch of stuff against the wall and seeing what sticks (which is exactly what was happening)—it just happens to be a really awesome golf course, so it's safe to assume that a bunch of stuff did stick.
With that said, I don't quite see it as the 5th best golf course in the United States, per the consensus of Golf Magazine/Top 100/Golf Digest. I'd take LACC or Pinehurst over it, and Merion is comfortably a better golf course in my eyes. I do think some of the criticisms in OP are fair, but there's not 15 (12?) golf courses in America better in my eyes and it really is cherry picking one of the world's best.
To answer OP's question though (and to avoid this being an Oakmont thread), Bethpage Black is what jumps out immediately, because nearly every ranking that comes out I'm shocked to see it as high as it is. The routing is good and from a tee-to-green perspective it is also great, but there's just too much wrong with it for it to be a top 30-50 golf course in America. On nearly every tee shot, the ideal line over the bunkers is just pure rough, and the greens are as flat as advertised. I get that they can't be so severe given the extreme nature of Bethpage's layout, but some interest—any interest—would be an improvement. On the other end of the spectrum, I'm not a Mammoth Dunes guy at all—to me, it's superfluous and lacking any true substance. I found that the choices off the tee were either a: set up a clear visual, or b: semi-obstructed visual into a catchers mitt contour, so I didn't really get much out of it. I much prefer Gamble Sands of that similar genre, there's a bit more strategy and drama IMO.
To make it an even 2 & 2 public/private, I really enjoyed Yeamans Hall but I never quite understood the World Top 100 placement. The green complexes are very good and the club is exceptional, but there are better inclusions for such an exclusive list.