Sorry if off-topic but I've seen many attempts at Qt bindings from Go and Rust. It seems all GUI libraries are more than 15 years old - except flutter, which is currently alpha quality on desktop.

As someone who has never implemented a native GUI library, what makes them so difficult to implement that we see so almost no language-native ones? Is it a matter of it not being monetizable, or something else?

Beyond the "this is too hard" responses (which from personal experience working on GUIs and toolkits for decades i think are overblown), it is also that a GUI toolkit -or any other library really- written in a niche language will only be usable for that niche language's audience but a GUI toolkit -or any other library- written in a language that can be used by other languages with almost zero friction, is way more likely to be used.

And people tend to use what they see other people using, thus repeating the cycle.

So you see these 15 year old libraries being used because other people are using these 15 year old libraries because they are written in languages that can be (relatively) easily be wrapped (both C and C++ wrapping can be done automatically and there are many tools for that - largely because this is something a ton of people want to do, so again, it feeds back to the cycle of things being popular because they are popular).

But there are lots of new toolkits being made, you can even find a submission for a new one in Hacker News almost every month (though the responses are pretty much the same in all of them :-P).

Accessibility and internationalization are really hard though, right?

I'm finally doing something about the accessibility issue: https://github.com/AccessKit/accesskit Still have a long way to go though.