Snobbism aside, I would gladly give up on some "usability" for a passive web (basically raw HTML or even Gopher or Gemini) and a separate active web (basically a proper virtual machine perhaps like Squeak/Pharo).
But as soon as you cut off ways to make the Web more "engaging", it makes it far less interesting for the ads market, so less contents. Even individual content producers (e.g. Youtubers, Twitchers) look for monetization these days.
AFAICT WebAssembly is in the continuum of HTML/CSS/JS, and is intended to "make things faster", so there is no reason to separate things that are essentially text and medias from things that are essentially programs.
In other words, WebAssembly won't cut the Gordian knot, in my opinion.
Are they? You still are in same infrastructure and legal framework. Thats like saying you are free not visiting neighbouring apartments. Their "influence" (smoke, noise) is still leaking to your space. Same with web. Like facebook negatively affecting separated web forums.