alt Hacker NewsI've noticed that developers who started with UIKit really have a hard time working with SwiftUI. I think this is because it's not just new syntax, it's an entirely different way to think: state is the source of truth, views are ephemeral, and you describe UI instead of managing it.
Apple has been adding Observable support to UIKit as well, so it's easier than ever for state to be the source of truth in UIKit too. Anyone writing more than simple UIKit apps has known that for a long time, it's just big a huge pain to actually implement without a lot of custom code or a dependency like RxSwift. If Apple had embraced reactive programming 15 years ago, SwiftUI would be UIKit's new layout system, not a whole new API.
Personally, SwiftUI makes the 80% so much easier that, even if the remaining 20% requires dropping down to UIKit, it's worth it.