MathML is a failed web standard
Blargh.  It annoys me that MathML was even a thing.  We've already had a perfectly-fine and widely-used markup language for mathematical formulae; it's called TeX.Ideally, I'd prefer that HTML5 include a  tag, or something similar, that takes TeX as input and produces formatted output.  A side benefit would mean that every browser, and every system, in the world would have TeX installed!At least MathJax can take TeX as input.