You can already build awful, non-semantic HTML today, with a giant pile of <div> tags, CSS, and JavaScript. The web hasn't fallen apart.
Similarly, just because it'll be possible to implement a full web engine efficiently in WebAssembly doesn't mean sites will suddenly stop paying any attention to standards or accessibility.
As for adblockers, I can think of several ways to block ads in such a world, including hooking the sockets API to block or sandbox access to ad-serving hosts, or providing hot-patches that stub out common ad-serving libraries. It'll get harder, but not impossible.
"The web hasn't fallen apart" for sighted users. Those non-semantic, unusable-to-screen-reader sites are in fact an accessibility disaster for blind users, who can find it nearly impossible to use some sites.
(And a disaster for the companies that build them and get sued later.)
Maybe there will emerge a common "screenreader toolkit" for sideloading a non-visual interface instead of expecting every designer to remember to interleave ARIA hints at magic places in an otherwise fundamentally visual interface, keeping it all in sync as the design evolves, etc.
> "The web hasn't fallen apart" for sighted users. Those non-semantic, unusable-to-screen-reader sites are in fact an accessibility disaster for blind users, who can find it nearly impossible to use some sites.
I'm saying that div-itis is possible today, but it's a bad idea, and as far as I can tell many new sites still use semantic markup when available.
Along the same lines, I would expect that even if people implement a web engine in wasm, many will still use semantic markup.
That said, I agree that people don't pay enough attention to accessibility, and should. But I don't think wasm or wasm-based rendering engines will make that worse.
Even if you use only divs, the actual text is there in UTF-8 to parse out of the DOM, today.
If you go all-in on wasm to do "your own rendering", external software won't know where to find a "DOM" or how to understand it, unless some other kind of reinvented HTML-for-a-wasm-rendering-engine-defacto-standard is invented?
(This is more a rant against "let's reinvent html/css in canvas" rather against a VM-based javascript replacement in general. Even though the latter sounds a bit terrible as well for the open web; imagine what the web would have looked like if .js never existed, and a flash/java .swf/.jar engine was the only way to do scripting in a webpage.)
What I can tell you for sure is that most sites are accessible to the extent that HTML makes accessibility the default, and the instant people start doing stuff that's not accessible-by-default (JS checkbox widgets, for instance), it almost always gets ignored and dropped.
So when you start talking about ignore-the-DOM stuff, my strong suspicion is that it would all be completely and totally inaccessible.
