The problem with MBTI is that reduces a continuum to a binary for each of the letters. IIRC, the basis for what each pair of letters means isn't any worse than any other personality test.
Astrology isn't about stars. It's about cold reading if done in person, and about the art of writing descriptions that sound specific but actually apply to pretty much everyone.
MBTI gives young people who are feeling lost a reassuring sense of self-discovery. Sometimes you just need a tidy four-letter label with a generic description to pretend to understand the chaos of your own existence.