E.g., we have an HTML datepicker now, but we're unable to easily style it. On Twitter a while ago Lea Verou (at least I think it was her?) advocated for a standardized autocompleting country dropdown, which sounds like a fantastic idea. We've been building web apps for over 20 years now, and at this stage there's a pretty rudimentary set of standard components, and we there are many for which having a styleable native component is long overdue.
In fact, it sort of seems like most things that have role attributes for a11y (e.g., modal dialogs) should have their own HTML elements by now.
I just found out about the datepicker a few months ago. I was incredibly happy to ditch JS for that.
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