Wasm in the browser can only communicate by going through browser APIs. Most ad / analytics / tracker blocking works by intercepting HTTP requests, so they will work just as well for Wasm code.

WASM that uses the regular DOM for rendering also doesn't really change blocking capabilities.

The only real issue is visual/selector based blocking when frameworks do their own rendering via canvas, webgl or webgpu. Flutter does this. But doing your own rendering comes with a lot of overhead, both in download sizes, startup time and performance.

Applications might do that (with lot's of caveats), but most websites never will. So I'm not that concerned.

Wasm is certainly much lower level than JS, but also much higher level than Assembly. It's far from an opaque binary blob. All the minified and partially even obfuscated JS is not that much better.