Earlier quoted context omitted.
That is due to the technologies available on the web being easily more suitable for GUI development than older native tools or desktop frameworks. We're in a similar boat, we made WPF apps. Now we're bringing it to the web and Electron. The things you can do now in React, heck i wouldn't even know where to begin in WPF or QT. If you look at modern Electron apps like Atom, VSCode, Discord and so on, the things they do…
Other than declarative vs imperative, please substantiate your post with examples of what isn't possible in WPF or Cocoa. I have a feeling it's more of an experience / competency issue rather than lacking APIs.
Debugging is also something different: https://camo.githubusercontent.com/a0d66cf145fe35cbe5fb34149...
Like hot module reload where you write your app live. You edit one component, everything else stays in place and maintains state. Or time travel with Redux, where each piece of state is inspectable. You roll back or slide through the apps history and see it literally build and deconstruct itself. That's possible because UI is just a function of state. Same state, same UI.