Having written actual apps with AppKit, it is horrendously complicated for simple things.

Swift is incredibly better than ObjC on so many ways it’s just not comparable. I used it since day one and never looked back. (And I was deep into the ObjC ecosystem, having written very low-level frameworks, and having loved it.) Yeah, first versions of Swift were raw, but now it’s just THE language; I used for everything (obviously Apple soft frontend, but also the web, the backend, etc. Even android dev I would do with Swift though I do not have the occasion for now.)

Apple will never drop ObjC support IMHO. But most new frameworks will be Swift-only.

SwiftUI is a step backwards from AppKit in the sense that we lose control over what’s possible when using it exclusively. But 1/ it’s much simpler for doing simple things and 2/ we can drop down to AppKit when needed. All in all, it’s good that we have it.