Sites using WebAssembly still need to use the DOM just like JS sites, and be equally ad-blockable. Technically a site could render everything as an opaque image

Sites using WebAssembly still need to use the DOM just like JS sites, and be equally ad-blockable. Technically a site could render everything as an opaque image in a canvas element, which would be hard to do ad-blocking on, but there's nothing about WebAssembly inherently connected to canvas elements. Whether a site uses WebAssembly and whether it puts all its contents in a canvas element are orthogonal issues. JS sites are equally capable of putting all their content in canvas elements, and very few of them do.