Who will develop a cross-platform UI system as capable, flexible and well-embedded as HTML/CSS and as responsive as native UI? Google did its shot with Flutter, it's not exactly eating the world. The performance issue will long be solved before somebody comes up with a capable contender.
> Who will develop a cross-platform UI system as capable, flexible and well-embedded as HTML/CSS and as responsive as native UI?
History shows that you can only choose one. If you're not using the platform's native UI stack, you're going to end up with a slower, less capable solution that will look and feel foreign and clumsy in comparison. What the industry really needs is a React Native-type solution that isn't tied specifically to React.
Trying to do that with Slint: https://slint.dev
No need to use compiled language like C++, still possible to use a language like JavaScript/TypeScript, just no need to bring a browser.