I gave this problem a stab a few years ago. I wrote an ascii-math derived language (but more powerful, and a little easier) called MathUp. I planed for it to be quick to write and easy to read (kind of like markdown for math). However it is not nearly as powerful as latex (and I don’t plan for it to be). Target are people that are writing quick math-notes (e.g. in class), or on forums where participants don’t necessarily know latex but might need to write a non-trivial equation or two.

https://runarberg.github.io/mathup/