TeX is to typeset mathematics as a shell script is to a specific set of actions taken by a computer. Neither come close to precisely defining the desired output

TeX is to typeset mathematics as a shell script is to a specific set of actions taken by a computer. Neither come close to precisely defining the desired output without a mountain of intermediate stuff that (a) needs to be present (b) can and does change and break things. This doesn’t mean that there’s anything wrong with TeX, it just means there are square pegs and round holes.