Did he actually say that? In this delightful interview https://conservancy.umn.edu/bitstream/handle/11299/107413/oh332dk.pdf in response to a question about were there any giant steps in CS, he says the idea of Structured Programming is a giant step but those are few and far between. A number of times he comments on structured programming (as opposed to HLLs). About Go To and SP: "It is like the zero population growth movement: The goal isn’t really to have zero population growth; the goal is to improve people’s quality of life. But they substitute a quantitative goal for the qualitative goal, and that’s like viewing structured programming as only a non-‘Go To’ type of a program, which is foolish, and I am sure Edsger didn’t mean it that way at all." He also mentions he wrote an Algol compiler for Burroughs during the summer of 1960. Knuth finished the first draft of what became TAOCP in 1966. Given that there were already many discussions about Algol X but no clarity and that he really did want people to understand what steps are needed and their cost, that is, get close to the computer, MIX made more sense (I'm glad it wasn't Fortran!). MIX wouldn't have made sense for TeX & METAFONT, which are in essence *recipes* made out of algorithmic ingredients and in effect he reimplemented these algorithms in Pascal.