I teach computing and used to teach maths. I agree with much of the maths content on the website of ACfE.
During the 1960s, school maths was modernised and became ideally suited to pre-university work. From the early 1970s onwards, much of this was replaced with utilitarian maths which had little structure and limited relevance.
Maths needs to be brought up to date, with the re-introduction of set theory, logic (used in computing), proof, synthetic geometry, matrices (used in computing), and so on.