Mathematical notation is highly ambiguous. See recent discussion of the alleged proof of the ABC conjecture (https://news.ycombinator.com/item?id=15971802 ). If it was really unambiguous then we could parse it like computer code and decide if it is correct or not without all the controversy about what it really means.

Well, mathematical notation is written for humans, not computers. With a bit of context, and comparing to human language (not code), it is very much not ambiguous.

Mathematical notation is not one thing; it is a whole poorly-specified family of context-dependent micro-notations. While I have spent my entire career enthusiastically educating myself on a wide variety of topics beyond anything I was exposed to in school, I have found it essentially impossible to learn any new mathematical notation beyond that which was taught formally. I am capable of understanding novel computer-science concepts perfectly well once they have been translated into a more accessible notation, and of putting those concepts into practice in my own engineering work; but as long as I am struggling through papers which express those concepts in mathematical notation, I understand little and get only as far as I can by inferring what the underlying abstractions must be from the surrounding English text. It very much is complicated, if you aren't already part of an academic system capable of passing it along to you, and so far as my experience has gone there is basically no other way to bootstrap yourself into it. I have spent rather more of my life educating myself outside any academic system than I ever did within one, so the value of a notation with such limited learnability strikes me as being considerably lower than what people who have made a career inside academia might naturally assume.