It wasn’t because mathematicians were reluctant to change that math in HTML didn't take off. Rather, it was because browser developers were loathe to implement and maintain the enormous and complex pile of code that is MathML, and they said "Why should we, if you mathematicians already have LaTeX?" [0]
Firefox has had MathML support for a long time. Complain to Apple and Google (and vote with your browsing activity, by using the browser that is less driven by commercial considerations).
Believe it or not, HTML, CSS, and MathML are still going pretty strong in the educational publishing industry.
MathType supports TeX input. MathJax accepts TeX input. The technology is already there, there's just very little mindshare because no one cares about accessibility.
[0] https://en.wikipedia.org/wiki/MathML#Browser_support