I am totally with you on WebAssembly, but I think this is a valid point that can't be swept under the rug.
Screen-readers operating against native applications aren't even close to their utility in browsers. Easy, reasonably universal text hooking is only possible on Windows and some OSX applications and while screen-fetching is universal, it yields extremely poor results in comparison to hooking. Very popular applications occasionally build Narrarator, sythesisprompt or NDK support but today "the web" (specifically HTML) is a much, much better experience for the visually impaired.
They only need to bring them along with the plugins, to what would become a portable framebuffer.