What do you mean about the MacOS UI? It sounds like you're talking about Stage Manager (which I love but understand not liking) but it should be disabled by default.
Some of this can be remedied with accessibility settings. Most things will likely stay broken until someone at Apple calls for yet another pointless redesign that will break something else in return.
That’s a hot take. Big Sur’s redesign is perfectly fine.
The only redesign I hate is Settings (especially since it disallows full screen, WHY?), but the rest is fine, and arguably less « in your face »