Isn't the distinction as simple as "does the language let you define anything and use recursion?", where I'm going to be a bit handwavy with "define anything" b

Isn't the distinction as simple as "does the language let you define anything and use recursion?", where I'm going to be a bit handwavy with "define anything" but I think we all get what I mean. You can't name functions in Brainfuck or recursively call them. You can do so in LISP and Forth. That is also the entire reason Brainfuck explodes in size: it lacks the "semiotic" capabilities required to compress source code (and therefore, structure and refactor code, which is what humans need).