That's why I'm saying it's box-ticking. Simple HTML is more accessible to everyone. That includes those with screenreaders and other content extraction/reformatting tools.
My understanding is all modern screenreaders (NVDA, JAWS, VoiceOver, etc.) handle JS websites perfectly fine and modern accessibility standards in JS are much more than box-ticking.
I'm a fan of simple HTML, too-but I don't believe it has any real impact on accessibility over JS with accessibility in mind. If there are specific cases where that is not true, I'd love to know them
If you think it's confusing to have a page change while you're reading it with your eyes, imagine what that would do to someone who can't see and relies on a screenreader telling them.
JS issues with accessibility is not inherent to the JS compatibility itself with the browser.
It’s much more that JS tends to make your page being modified in unexpected ways. If all you have is a voice reading the page, you may be submerged by information each time the dom changes and you may have a hard time understanding what is the context of the element which changed.