https://www.w3.org/WAI/ARIA/apg/patterns/ is my go to for accessibility requirements of components.

And yes, being able to do all of these in pure HTML/CSS would be awesome. Though we are getting there with things like `details` and the newer `popover` features which should make things like rich tooltips, menu buttons, etc. a lot easier to implement. IIRC, there are also several anchor CSS properties to make positioning a lot simpler.