As a contributor to RN and someone who loves SwiftUI just as much: it’s mostly the toolchain. You have an unbelievably vertically integrated framework with SwiftUI.

Sibling comment here mostly covered it, toolchain is kind of all over the place and build times are way faster with swiftui on my 2015 MacBook.

Also with Combine and associated bits there is a lot less boilerplate around state that doesn’t have to be written.

Also the disk space for the js ecosystem is beyond crazy and really bothers me.

Compared to native development the toolchain and dependencies are out of control and I'm unsure how it can really be improved, Expo does a decent job of abstracting some of it but you lose so much from the managed workflow that it makes me question the purpose of building a native app at all. I think the real threat that PWAs bring is to frameworks like React Native and Cordova rather than fully native apps which will likely always have specific use cases.