Simply watch the Blond Ambition Tour and you'll know the answer.
No, her vocals are not very good, it's quite irritating sometimes tbqh - but her talent is much, MUCH more than just vocals.
Just listen to her discography. I'm completely fascinated about her playing with images and sounds, experimenting, pushing boundaries...
I didn't use to care about her, but when I got Celebration (the 36 tracks version), I was simply amazed. So many classics.