I’ve used OSX on Intel since Leopard (10.5), though I have a Jaguar (10.2), Panther (10.3) install on my old PowerBook and Tiger (10.4) on my G4 Mac Mini, and small things changed, but on the whole the OS is the same. I mean, Aqua style changed massively between 10.2 and 10.5, so there are arguments that the UI might have seemed better to some pre Intel. For me, Spotlight, Exposé and Spaces made a massive difference and that is what I miss most when I have to do something on a legacy install. Even Tiger is painful to use because of missing Spaces and Exposé.
I use Monterey at the moment on my main Mac and it’s absolutely fine.
Possibly the lack of spaces? I use Exposé mostly to organise my spaces these days. I use older OSX less and less as PowerPC is only useful to developing the retro68 port. Since I got Sorbet Leopard on the G4 it also hardly boots Tiger.
I use Monterey at the moment on my main Mac and it’s absolutely fine.