It fits for software that has not reached its creators stated goals. LLMs are not AI and have not improved lives for any human, outside of making some people rich.
I'd disagree the definition fits that situation as vapourware is for software which is still unobtainable, not software which is available but the reviews and feature coverage suck vs the advertisement hype. Are we able to talk about that definition further before we dive into talking about your views on LLMs?