I wonder if at any point browsers will offer a low level accessibility API for you to manually describe components. I’ve worked in the web for years and I’m a big believer but it’s also indisputable that Canvas offers more performant UI rendering than HTML when done correctly. I don’t think it should ever be used for web “documents” but web apps already bastardize HTML and CSS to achieve their aims anyway. Accessibility remains the missing component.
It's HTML imagemaps from the 90s, when we could not style buttons and navbars where GIFs with links in the right places. Browsers still have the code to render them.
OTH, we are still failing to provide a bare minimum for accessibility. Heck, we even needed a law (in the EU, that than needed to be translated to national law), so that companies providing crucial end user services would care about accessibility.