https://www.swiftlatex.com/editor.html for the wysiwyg editor says "We are working hard to fix the editor." It has said this for many years. I think I tried it once when it was live and it was pretty cool. My guess is people observed it could corrupt documents, so it was taken down.
Over the years many people have hypothesized that once WASM was really mature, it would become practical to fix the issues with web browser layout by sending down custom layout machines to users.
I would find it hilarious if LaTeX turned into a leader in that space. I doubt it could hold on to that. There's a lot of things that something designed from the beginning for web-like uses could probably improve on that would be capable of overcoming LaTeX. But I could see a world where it carves out a niche and holds on to that niche for a long period of time.
I feel like it's fair to say that you have not "fixed the issues with browser layout" if you lose accessibility and input. System fonts I can live without, we can push our own, but those two things are a big deal.
Even input you might be able to hack around but accessibility is a big deal and the "hack" at that point is nearly to both lay it out in the browser and the supposed "fixed" layout system, and while that may work in some sense I again have lots of questions about whether that is really "fixed".
Add LuaLaTeX and you're cookin' with gas. For real would be fantastic if we could get more or less the full LaTeX ecosystem readily and rapidly available online and in a huge variety of desktop applications.
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