Even though we have many gaping holes in the details of the current UI due to the many paradigms (SwiftUI, AppKit, Catalyst), skin-deep macOS is much more agreeable.
Cocoa apps are mostly fine in modern macOS. Their main issues are the lack of contrast*, but things like the dark theme are great. From what I have seen SwiftUI is fine too, although it still has some way to go to catch up with AppKit, and has some rough edges. Catalyst is plain garbage, though.
* a pet peeve: I have to click 3 times when I want to make sure that the shuffle mode is either on or off in Music. Another one: document proxy icons are getting hidden and harder to use, even though they are a fantastic feature of the OS. There's a bunch of others features that are becoming more and more obscure, which is a damn shame.