There's still plenty of high-quality Hip Hop being made, it just isn't what sells to mainstream audiences. Gotta do some digging to get the good stuff, and most people don't have time for all of that. Nowadays, you have artists like
Conway the Machine,
Freddie Gibbs,
Westside Gunn,
JID,
Mick Jenkins,
Kendrick Lamar (of course), and if you like the really lyrical stuff, there's a new style popping up on the east coast called Drumless that focuses purely on lyricism. Some of the best Hip Hop writing I have ever heard coming out of this scene. Some amazing artists include
Ka (my favorite Hip Hop artist ever),
Billy Woods,
Mach-Hommy,
Estee Nack,
MIKE, and
Earl Sweatshirt. I agree that mainstream rap is mostly ass nowadays, but I have also never seen the underground Hip Hop scene so vibrant and full of talent ever before.