This notion that you can only have DOM/CSS/Javacript on the web did not age well. There's a whole generation of programmers that built their careers on targeting that and are confusing that status quo with something that is set in stone for good reasons. Those reasons never really existed. Javascript was a bit shit but it was there so people used it. Fast forward 30 years and you still have people proving that point on a daily basis by creating very mediocre and underwhelming things with it.
WASM opens up the web to 30 years of progress in UI development elsewhere (mobile phones, game consoles, VR/AR, desktop, etc.).
What people will do with that is of course an open question. There are a few frameworks emerging but they are still kind of niche. And there are lots of attempts to bring retro UIs to the web unmodified. Links to e.g. Winamp in a browser, VB 6 running in a browser, etc. are easy to find. Some people even boot entire operating systems in a browser. I think I came across windows 95 at some point. A few versions of Linux, and some other stuff. Cool, but I'm more interested in new stuff.
The web has bit of an imagination deficit. Creativity on the web mostly died along with Flash. HTML + Javascript never managed to fill that void. Just the wrong tech for that job.
