Plus, Knuth, despite his accomplishments, is a terrible computer scientist and programmer in some capacities. TeX must be the most odious language not designed as a deliberate joke.
TeX is not a "language"; it's just a tool for typesetting when you want to go the last mile of achieving book-quality printing. The fact that it turns out to be possible to (ab)use its macros (originally designed merely to save the user some typing effort) to do "programming" shows only that it's easy for things to become "accidentally Turing complete" [1], and the cleverness/perversity of its user community.
> TeX was designed for typesetting, not for programming; so it is at best “weird” when considered as a programming language. — DEK, Digital Typography, page 235
> In some sense I put in many of TeX's programming features only after kicking and screaming. — DEK, Digital Typography, page 648
> So TeX is a programming language but I had to put in those features kicking and screaming. […] In a way I resent having every language be universal because they’ll be universal in a different way. […] I was really thinking of TeX as something that the more programming it had in it, the less it was doing its real mission of typesetting. When I put in the calculation of prime numbers into the TeX manual I was not thinking of this as the way to use TeX. I was thinking, “Oh, by the way, look at this: dogs can stand on their hind legs and TeX can calculate prime numbers.” — DEK, interviewed in Peter Seibel's Coders at Work
> Michael Plass, who was Don's student and worked with Don on TeX, told me once that "Don tried very hard not to make TeX a programming language. Unfortunately, he didn't succeed." — Norman Ramsey
I've written more about this verbosely elsewhere [2], but in any case even if TeX had been intentionally designed from the start for public consumption (rather than for just him and his secretary, as was his original intention), it hardly justifies something like "terrible computer scientist" — TeX/MF/CM was just his side-project; the computer science is different.
