One day you might be able to do that. The current spec for WebAssembly doesn’t let the GC see the stack, which is a deal-breaker for “good GC”. So for the time being, compiling to JS is certainly a much better option — also much better for accessing the DOM, which is of course vital.
Perhaps I just see everything through “GC-glasses”, but the way garbage collection in the DOM and JS work together is pretty complicated and relies heavily on the JS VM being trusted code. I’m not sure how you would _ever_ replicate that in WebAssembly, so I think transpiling to JS is going to continue to be the best option for any GCed language on the web.