Anyone remember this video? https://www.youtube.com/watch?v=UuLaxbFKAcc - Totally Gridbag

As others have said, JavaFX is really pretty good. People who use JavaFX generally seem to be satisfied, it's not often I see a substantive criticism of it, but unfortunately it seems to be widely regarded as too little too late and doesn't get given a chance. The Ada of the GUI toolkit world.

Unfortunately had issues with new version breaking backwards compatibility etc. which killed it.

QT also had similar hype but never took off.

I wouldn't build a production application in WinForms, WPF and friends are much better for that. But, for quick&dirty or even moderately complex tools for experts, VS + WinForms simply has no equal. Some Python-based designers come close, but they definitely suffer when it comes to distribution.

With modern dotnet tech, Microsoft could allow us to build a (rather sizable) single, statically linked binary for any architecture, with the impressive performance of the dotnet JIT and native controls.

After working on Android designs, I've got to say, XML is fine for UI design. You need previews and visual inspectors to get an accurate idea of what you're doing, but describing what control lives where and what properties it has is a perfectly sensible use case for XML.

We'll be writing WinForms applications in the 22nd century.