Compared to Windows? Tahoe is probably fine. Compared to previous versions of macOS/OS X? Nothing deal-breaking for me, but there are all kinds of little things that just don't have the polish long-time macOS users are accustomed to. Sibling comments have already listed a few things, but take the grab points of the window corners, which don't actually match the window borders. A minor thing, IMO, but not very "Apple-y" to let something like that ship. The menu icons are another: they add clutter, they don't add a lot of value, and they look like crap. Again, not a huge deal, but c'mon, Apple, UI is supposed to be your thing.

I don't hate Tahoe myself, but I don't particularly love it, either. I can still get done what I need to do with an OS, but along with a bunch of other paper cuts in recent macOS versions (looking at you, System Settings) on top of Liquid Glass, I can see why folks are upset.