I'm in the same boat. I was asked recently to develop a small custom app for a library that would need to be maintained for decades. This left me scratching my head as to which GUI technology to choose to minimize the danger of it being broken/unsupported after 10 years. Paradoxically, I think Win32 might be the safest choice as MS can't really innovate (=break) too much here anymore (although I might underappreciate their skills in this regard).

Emacs Lisp would probably rank even higher.

Or DOS. You can run DOSBox on anything including a web browser.

Parent said GUI though.

You can run GUIs on DOS. A lot of DOS software had GUIs.

Yes. I would argue that it is precisely the obsession with cross-platform that has destroyed native desktop applications. If all you are offering with your native desktop framework is a dumbed-down experience, because it has to also run on tablets and phones and TVs and game consoles and smart refrigerators, then you quickly get to a place where there are few advantages in going native over shipping a webapp in a Chrome wrapper.

Windows 8 was a catastrophic failure, and Apple seems to be leaning into the same failed philosophy now.

It is not really "obsession", it is economics. There is a high cost with maintaining different apps for different platforms.

“and Apple seems to be leaning into the same failed philosophy now.”

I agree but when you look at their profits it seems MS and Apple are doing the right thing even if I don’t like it as a developer.

Well that's all well and good but it doesn't explain why even Mac OS devs are moving en masse to building for the web.

Mac devs have been complaining for a long time that Xcode and the entire developer experience sucks. It sucks (1) in the way that most native development sucks, and (2) an extra layer of suck on top of that.

The Mac platform also used to be very insulated; the culture meant that the prospect of creating an app or simple utility and selling it was viable much longer than it was on Windows, where the culture is that everything is either gratis-style free or warez-style free. The invasion of the Web means that Mac users are increasingly being conditioned to get things for free, too, so the viability of paid apps has taken a big hit. SaaS is the way to make money now.

Maybe they want their programs to be useable by non Mac users too?

SwiftUI keeps breaking stuff constantly.