A lot of the rappers back then had crossover appeal to other fanbases/genres of music. These new rappers are lacking that when it comes to both sound and lyrics.That just shows his (predominantly young and black) fanbase doesn't pay for streaming services. His youtube numbers are very high but they don't count towards charts as much as paid streaming.
In terms of hits....Drake had a hit (Nokia) this year, Kendrick has had the biggest rap song this year (Luther) and last year (Not Like Us). There have been hits. The issue is Drake and Kendrick are in their mid 30s. I'd argue rap has gone through a lot of misfortune that has led to a generation missing. X/Juice/Pop dying killed off the next big three. Uzi/Kodak/Carti becoming drug addicts has removed potential hit makers from the market. Then the Thugger fukkery has indirectly led to Baby falling off and Gunna not being as big as he should be. In the void we got a lot of thot rap but that shyt was never going to last.
It also seems most of the young gen into Hip Hop is listening to rage music, and I don't think that type of music will ever be any bigger than what it currently is.