I use Flutter for some web apps, it works fine. It's good for web apps, not web sites, and compared to other desktop or mobile apps, there is literally no difference between rendering on a canvas to rendering on Qt or SwiftUI. People, in my experience, just get up in arms about the web that does not happen with other technologies.
Do you realize that Flutter has an accessibility system that is often more advanced than most desktop UI frameworks? [0] I notice this often from non-Flutter devs, Flutter has some pretty good a11y.
I don’t know if even that was actually true? As far as I know the moment they introduced canvas as a rendering target they also produced a DOM structure along side it to capture the accessibility tree as they were still waiting on a more native solution in the form of AOM (accessibility object model) to be finalised.