Why does mainstream R&B today suck?

In the 1970's you had all these great musicians that appeared on Soul Train like Marvin Gaye.Stevie Wonder,Aretha Franklin,Gladys night,Labelle,The O jays,the isley brothers,Bobby Womack,Tina Turner,Teddy pendergr,Al Green,KC and the sunshine band and so on and I think that the comemmercialization of Disco ruined it and when Disco got destroyed R&B became contemporary R&B using electronic instruments and then when hiphop got its own beat then R&B changed too and I think that ruined R&B and do you think if hip hop never existed then music period would be better?