That is, the closer to HTML the better.
Plain javascript is a crappy way to represent HTML because both the syntax and semantics are different (and sometimes there are conflicts, like with "class").
JSX is better than plain javascript because the syntax is closer, but the semantics are still Javascript, and there are still a number of differences you need to work through.
svelte is even better, because the HTML parts are strictly character-by-character the same as HTML, but you still need to know the syntax of a few escape mechanisms.
If there were a way to improve significantly on svelte then I'd be all for it. (Maybe HTMX? I'm skeptical of the approach of putting a network round-trip into every UI interaction, but they sure have nailed down the HTML aspect of it.)
Since all of this is client side (and display: none; is the best you can do in terms of not revealing everything to the user anyways) you don't even need any behavior language in HTML. Just set classes to elements and manipulate them with the framework from outside.
