The support for #MathML in browser is often poor. The fact that instead of improving it the developers seem to be instead pressuring the standard bodies to impoverish the language only makes this worse.
(I am aware of #MathJax. We shouldn't need a heavy-duty #JavaScript library to solve typesetting problems. That's exactly what browser engines are there fore.)
I weep for the status of scientific publishing in the modern world.
(This rant is offered by my experience looking for options to make the SPHERIC newsletter available both in PDF and in HTML form. I don't even need complex math usually,, we try to avoid it in contributions because it's hard to typeset math outside of the TeX world. But the fact that in 2026 online the only safe way seems to be to typeset everything manually or rely on huge JavaScript libraries is a little depressing.)