That still requires more tooling.

It is a little unfair since LaTeX has tons of extra libraries involved. It’s probably been more than 5 years since I touched LaTeX, but I usually (if I remember correctly) used amsmath, babel, biblatex, inputenc, fontenc, hyperref before I even started.

I don’t think it is unreasonable to ask authors that insist on writing in familiar syntax, that they use a tool that enables that. With native MathML authors are free to use whichever tool chain they prefer. Some authors will prefer graphical editing of equations, so they have their authoring tools set up that way. Others will just want to write their familiar latex syntax so they’ll put a:

    <script src="./path/to/texzilla.js"></script>

in their document and write as before.