Whitney, Mariah etc are fantastic, however the type of ballad music they were doing would not work today. Both Whitney and Mariah realised that as well, which is why both started drifting towards Rnb in the later years of their careers in order to try and stay more current. Mariah's last album was still fantastic, but she's achieved in her career pretty much all there is to achieve so she is now at the stage where she can release the type of music she wants to release and not have loads of pressure on her.