If you mean due to lack of C++ for doing GUIs, Google and Microsoft have also long left C++ to the dust, in what concerns GUI frameworks.

Even Microsoft, for all its C++ use, has never produced anything better than MFC to this day, and only Windows team cares about XAML C++, others rather use React Native or Webview2 alongside C++.

It is up to third parties to use frameworks like Qt.

I mean specific APIs and targets are required to be written in Swift (e.g. widgets) + iOS/macOS dev tooling is hostile to any attempt at bringing in your own preferred language stack. I wouldn't be surprised if Apple's "glasses" or other tiny devices make it even harder to stray from the "one true path".

No different on Microsoft and Google platforms.

Those that think it shouldn't be, end up yak shaving trying to bring UNIX and C concepts to platforms that no longer care about that.

How is it hostile?

Calling ObjC via your language of choice is like the easiest thing possible, solved multiple times over. Signing and notarizing outside of Xcode is also a solved problem.

IME people bitch about this but when push comes to shove just don’t want to do the required work, typically on flimsy grounds. It’s just not that hard.

The increase in Swift-only frameworks will eventually be a problem but it’s typically not a blocker right now.

Swift and SwiftUI on macOS are the most complete UI framework that is native, fast, performant and works very well.

Basically no other platform comes even close in terms of ease of use and performance. The best would be to extend that kind of framework on Windows (and/or Linux) and make it work same / similar.

Funny that you mention performance

> For instance, Apple's SwiftUI is reportedly slow[1][2][3][4],

I've never used SwiftUI (nor Apple platforms) personally but I find its approach elegant.

This is an attempt to build apps with SwiftUI idiomatics https://aparoksha.dev/ (blog on it here https://www.swift.org/blog/adwaita-swift/). It's implemented using SwiftUI on MacOS, WinUI on Windows and libadwaita on Linux.