I can't speak to "most", but the incredible CrossCode displays the HTML5 shield on startup, so indie games on the web stack do exist and can be amazing.
Yeah the browser is sadly underused, especially for indie games. Js is plenty fast for most indie games, there are a ton of libraries, dev tooling is good, and all the APIs you could ever need are wired in. There's also an 'escape hatch' with WebAssembly for better performance when you need it.
I would be surprised if you can find any platform with graphics output that someone hasn’t published a game for. Having one game says nothing.