I'll believe that once I see you file an issue which mentions accessibility against any of the projects I linked to ;-)
https://github.com/facebook/react/issues?q=is%3Aissue+author...
https://github.com/vuejs/core/issues?q=is%3Aissue+author%3As...
https://github.com/sveltejs/svelte/issues?q=is%3Aissue+autho...
Simon don’t waste your time with this guy. I thought he was affiliated with htmx but he’s just some dude trying to prove he’s “right”.
Now if you say that component frameworks like shadcn/ui or whatnot should implement accessible behaviours and patterns, I am 100% with you on that. But React/Vue/htmx are at a lower level, they can't decide those things for you.
EDIT: sure enough, someone filed an issue with shadcn/ui that it does not announce something properly in screenreaders: https://github.com/shadcn-ui/ui/issues/4209