If you're comparing Rap to Jazz, 80s and 90s Rap music was free-form, inventive, improvisational. There was a similar niche market.
But now it's a formula like Pop music, it's mass produced for the younger generation and along with that comes the fashion so your kid can look like his favorite thug. IMO, this mass-marketed formula not only includes music that sounds the same, but all Rap artists now look the same.
I can understand how Rap music and it's fashion is so popular, due to some very smart marketing people, but I cannot understand how Hollywood and celebrities embraced it.