It's mindblowing that there's no modern LaTeX replacement. I've seen talks about it at https://hackpad.com/New-scientific-markup-language-utAjFcYuv..., but nothing came out of it. Something with a saner syntax (think markdown), a modern interface for nontrivial tasks (maybe pythonic), better extensibility, cleaner codebase, better error msgs.... There would be millions of users instantly, but it's probably a gigantic task. Someone do it, please