SVsvat·Oct 14, 2023
The point of MathJax is so that users can type math the way they are used to—typically TeX syntax, though MathJax also supports AsciiMath and MathML itself—and get nicely typeset output (MathJax has three output formats: MathML, SVG, and HTML+CSS). At most you could say that MathJax's MathML input and HTML+CSS output are no longer needed, but that's not the bulk of the need that MathJax serves. Also:
1. [Input] Even if only targeting MathML output, you still need some way to take the user's TeX input and generate MathML, which is what MathJax provides here. What are the alternatives to MathJax that you have in mind? The closest competitor I'm aware of is KaTeX, and while it is fast when it works, there are still some holes in its support (relative to MathJax). (Another comment in this discussion points out Temml, which indeed looks good:
Read the rest
https://temml.org https://github.com/ronkok/Temml https://temml.org/docs/en/comparison.html )
2. [Output] The MathML output rendering in browsers is not yet 100% identical to TeX's typesetting (they're certainly aware of it / thinking of the right things, looking at the mentions of [TEXBOOK] at https://w3c.github.io/mathml-core ), and this may even be intentional. In particular, looking at various MathML demo pages I found online (http://eyeasme.com/Joe/MathML/MathML_browser_test.html https://fred-wang.github.io/MathFonts/mozilla_mathml_test https://www-archive.mozilla.org/projects/mathml/demo/texvsmm... and Temml's useful demo pages: https://temml.org/tests/wiki-tests https://temml.org/tests/latexml-tests https://temml.org/tests/mozilla-tests) it appears that in all three of Chrome/Firefox/Safari the rendering of nested square roots is a bit suboptimal, while Safari has some more serious issues (example 9 of the Mozilla MathML Test
looks poor in Safari). But clearly the Igalia (for Chrome) and Mozilla folks have done great work, and it's pretty close, but in the meantime I imagine at least some authors would prefer the more deterministic (across browsers) output of SVG or HTML+CSS.
(Also, on a lot of these MathML demo pages, selecting and copy-pasting the math produces junk, while with MathJax there's a right-click menu providing the TeX source and also some accessibility options… it seems that accessibility is actually higher with MathJax under certain circumstances at least.)