[nailer]

> I'm glad that a large proportion of web developers are happy to boil the ocean then.

That’s not how that expression works. The ocean is every website. An individual developer cannot modify every website.

More to the point, most websites are not accessible, will not validate, and this will never be the case.

[RobMurray]

It's not a binary. most web sites are accessible to some degree. Just the fact that semantic elements exist at all makes a big difference. Popular frameworks have accessibility built in.