Not that this accusation is deserving of further thought, but lets look at the premise.
Beyonce I believe just came off a 100 million dollar tour, Rhianna and MJB were multi-platinum in a sagging sales market. Tyra has 2 highly successful shows, Latifah has about 4 major endorsement deals and thats off the top of the head.
All of the aforementioned stars had to have crossover appeal to achieve that level of success and marketability. The premise of the accusation is so flawed that its laughable.