They will always be relevant no matter how many times their albums and singles flop, they're beyond Billboard, Mediabase and Mediatraffic at this point.
People trying to discredit Mariah's legacy when basically all of their faves have been praising her, this goes especially for Beyoncé, Rihanna, Christina, Britney and Katy. Gags aint messing with ha either
I think legends such as Madonna and Mariah will "always" be relevant as their legacy lives on through new generations of pop girls.