Earlier quoted context omitted.
If you're an actual mathematician writing pages and pages of equations, LaTeX is not complicated, unintuitive, ugly, or slow. It's actually extremely well designed for addressing what is a very difficult problem, the problem of translating mathematics into ASCII. For how difficult that problem is, LaTeX is quite genius. I think a lot of the would-be LaTeX-disruptors lack enough experience actually writing mathematics…
But what if you a computer scientists or an economist that needs to write graphs, charts, tables, code, etc? Last time I tried to strikeout a column it required some weird TikZ shenanigans.
On the other hand:
* For graphs and charts, I'm not sure how it could be done much better in a text-based programming language.
* Even for tables you have to have some sympathy because remember, the cells in the table can (and occasionally do) contain very complicated mathematical contents. Tables are hard, as many a frontend dev will assure you.