I think MathML might not have failed so hard if it weren't so ludicrously verbose and time-consuming to type compared to TeX notation. XML apologists generally

I think MathML might not have failed so hard if it weren't so ludicrously verbose and time-consuming to type compared to TeX notation. XML apologists generally propose special editors to make the experience less unpleasant, but that's not what working users of mathematics want. TeX notation provides a way for us to type formulae in plain text form, anywhere that ascii is accepted, as fast as we can type normal text. That's the bare minimum required for any representation to be relevant to mathematicians and physicists. I don't know what a more 'web flavoured' notation satisfying this constraint would look like. (Are web standards people even capable of brevity?)