Cultural appropriation is about exploiting a culture. Not every non-black person who does hip hop/R&B or every popgirl who does an urban song is appropriating. What Gaga did is just doing something different/hopping on a trend etc. What Miley is doing however is a classic textbook ex. of appropriation, and I would argue that would Gwen did with the Harajuku girls who never talked was also exploiting as well.
JLo doesn't get her due on ATRL. She's like the better version of Britney.
She doesn't get her due because she doesn't deserve any. A few cute bops here and there, but so did Paula Abdul, Jody Watley and Avril Lavigne. Where are the praises for them? She gets what she deserves... little to nothing.