It is a legitimate issue.

But it also doesn't cause the developer enough pain to register as a priority. The market is telling you something: it either isn't painful enough to spend money on, or you're not reaching the right people. IMO, you can sell to developers, but you have better luck selling them something that feels like it gives them a superpower, e.g. React is an easy sell because:

1. Reactive binding burns away a lot of imperative state-changing code

2. Facebook branding implies it is industrial-strength

And even then, React costs them their time to learn, build on, and ship. If it's their company's time, then they're not going to value it the same way.

For everything you think someone else needs to care about, there are probably a 1000 other things as well.

It's not necessarily if people care but what they care more.

You have solved the problem of the considerable "extra" effort that web accessibility requires? Less than that, to be honest I'm not interested. If you have, well, extraordinary claims require extraordinary proof. Would you say that you have extraordinary proof?

Reading this back to myself, I think that I sound like an asshole, but it's my honest thought process fwitw.

It's true. The challenge is developing in a way that covers the wide range of human disabilities (e.g. vision to cognitive). WCAG will continue to evolve to try and capture the full range. That range of disabilities is why manual testing with a screen reader and a keyboard is the current best solution for uncovering edge cases where a website, or mobile app, is inaccessible.