I think it is fair to point at a paper where Van der Hoeven argues in detail in favor of the WYSIWYG paradigm:
J. van der Hoeven. GNU TeXmacs: a free, structured, wysiwyg and technical text editor. In Daniel Filipo, editor, Le document au XXI-ième siècle, volume 39–40, pages 39–50. Metz, 14–17 mai 2001. Actes du congrès GUTenberg.
For why so few people use TeXmacs, it may be that it is because few people believe that it is worth trying, as one would not expect that it works so well :-)
I think it is so. As far as I know, there are no converters that can do that. A search with an LLM made me find https://arxiv.org/pdf/2605.16562, a paper describing the ArXiv conversion tool from LaTeX to HTML; here is a sentence from the abstract:
"corpus-scale conversion work aimed at 90% error-free HTML (currently 75%)"
although there may be issues that I do not understand or did not see (I looked at the paper very quickly) that make it more difficult for the authors than for the simplest possible translation.
While Typst appears to be popular, I think that TeXmacs, https://www.texmacs.org/, which is a program independent from both TeX and Emacs, is the kind of program that we need for writing: a fully WYSIWYG, fully structured document preparation system, in which you edit the structure of your document in a WYSIWYG way.
When editing the structure on-screen, the user has no need to be aware that is doing so, as it looks like they are editing a text document; at the same time, the TeXmacs editor will guide the user to keeping a structured document.
There is some support for the LaTeX ecosystem from within TeXmacs. If you want a TikZ drawing, you can insert it programmatically into a TeXmacs document in a seamless way---if you have the same font for your TeXmacs document and for LaTeX it will be nicely integrated as far as I know,
You can see the blog post
https://texmacs.github.io/notes/docs/embedding-tikz-figures-...
I use it for all of the pedagogical material I distribute to my high school pupils. It allows me to type quickly and accurately math and explanation with exquisite typography. It allows me to edit freely and with total ease what I have already written: I don't have to look for the point where I have to edit because it is WYSIWYG.
I do not have to collaborate with anyone in writing so it does not matter that there are no users among my colleagues.
In my opinion it is superior to all other systems I tried (I tried many and a lot, and all of the main ones). And, importantly, it is equal or superior to the other systems in _all_ respects.
I would rather use TeXmacs, it frees you from the write-compile cycle while being equivalent (maybe in some ways better) from the point of view of the control you have on the document and the typographical quality.
J. van der Hoeven. GNU TeXmacs: a free, structured, wysiwyg and technical text editor. In Daniel Filipo, editor, Le document au XXI-ième siècle, volume 39–40, pages 39–50. Metz, 14–17 mai 2001. Actes du congrès GUTenberg.
Reproduced at https://www.texmacs.org/Data/TeXmacs.pdf
For why so few people use TeXmacs, it may be that it is because few people believe that it is worth trying, as one would not expect that it works so well :-)