Indeed completely missed that. Of course, the web needs to work on safari and firefox as well. So, it doesn't quite address the core issue here.
The big issue is that MathML is designed as a target language, not something directly writable. So we still need a KaTeX equivalent, which compiles either LaTeX equations or other markup languages to MathML.
Regardless, the core issue that you have mentioned is now gone (or will be in a few years even if you want more availability).