@shutupuface. Most critics/scholars put August 11, 1973 as the beginning of Hip Hop, when DJ Kool Herc was the DJ at his sister’s back-to-school party. Just like any other genre (punk, rock, country, etc.) there is no definitive start date. Most genres obviously don’t start with the artist calling it that from the beginning, but are usually branded over time by fans, critics and record labels.
As usual with these threads, the original OP’s question (if artfully stated) has devolved into old white guys sounding off on something they don’t know that much about. [to a degree, myself included]
As I read the original question, why has there been no new, popular genre of music that has lasted since Hip Hop?? Yes, as other posters have pointed out, there have been 100’s of genres and subgenres that have bubbled up, but nothing as massive or long-lasting as Hip Hop. I believe that has more to do with the way that popular entertainment and music consumption has become so diffused. There is no definitive source where (general speaking, young people) congregate to get their music entertainment.
MTV and then commercial radio was a key developer for popularizing Hip Hop. Once could also argue that the channel acted as a gatekeeper to hold back the genre from exploding more in the 80’s. There is no such go-to place today. Commercial radio is strong, but doesn’t really set trends anymore for younger listeners, they follow.
Also Hip Hop has lasted (and yes evolved) because it is much more than a music genre. It's an culture, attitude, fashion, political stance...in films/TV, sports, etc.. Like rock n roll, it has evolved and gone mainstream and seeped into every aspect of our society. And please don't chime in that it's not your style...that's the point.