And yes, I agree that it's a useless definition. I've never seen it used outside of esoteric political debates.
Esoteric? It's a central concept for understanding how capitalist societies are structured. The central concept, even. It's not math, it's language, exceptions or hard-to-pin-down boundary regions don't wholly invalidate or render useless an idea.
That might be fair. I wouldn't consider a term well understood by anyone with much exposure to the social sciences (any of them, just about, will run you into it, sooner rather than later, probably) or a more-than-tiny exposure to economics (if we're feeling generous and separate that from the social sciences) or just about any higher liberal arts education, to be esoteric, but I can see that falling within one's tolerances for the term, depending. Probably well North of half the population would be lost by it, or take something other than the intended meaning, that's true.