Then you can only have islands of either paradigm within each other. UIKit and SwiftUI do indeed compose, albeit coarsely.
I can't blame them, they got influenced by react. Don't even blame react, it was a good attempt. Basically trying to build a UI from a snapshot of a tree. Except this is too simplistic a model. They designed it as if you could equate the number of games and the number of positions in chess. Like a markov chain. Except playing chess has side effects. A mere snapshot does not encode those.
I understand the mistake.