Comment by acdha

That's effectively closing off a growing percentage of modern life from people with visual impairments unless you think that places which chose not to follow good web practice would be much better at publishing data to an API they use even less (Googlebot at least used to help accessibility because sites which were all Flash/images/JavaScript wanted to get indexed even if they didn't care about being accessible).

I would also reconsider why that “API” would be better than the existing web APIs which the community has been working on for the last few decades. HTML is great for this purpose: you have a rich document markup language with a decent semantic model, separation of display styling from content, and the ability to add metadata to support different accessibility modes. Using it to build applications is problematic but still possible: the main problem being that many JavaScript tools are developed by teams which don't prioritize accessibility, which is really the same problem as the previous paragraph where things which the people building the site don't check tend not to work. That's getting better but it really needs a combination of awareness of the need and legal ramifications to get people to build it in from the beginning.