Term for someone in the entertainment industry that people will pay to go see or watch on the screen, despite the fact that said person can't really sing, play music, act or do anything else noteworthy. Because they don't really sing, perform music or act, they can't
legitimately be called singers, musicians or actors. 'Performer' is a nice
catch-all term for such people that doesn't demean others in
the entertainment business with actual ability.
Note that the mere fact that performers have no particular ability doesn't mean they can't make plenty of money doing whatever it is that they do. The one ability that performers generally have is marketability. And as countless examples have shown, the ability to be marketed (and to market one's self) is far more important than musical or acting talent anyway.