I wonder if it's linked to the average American's attention span decreasing. The average American had an attention span of 15 seconds in 1990, 12 seconds in 2000, and only 8 seconds in 2016. Maybe the teenagers/young adults of today like that retarded rap more than lyrical rap because they actually have to kind of pay attention to lyrical rap.
Even me, I find myself liking some of them retarded rap songs like 21 Savage, I wouldn't have been caught dead listening to that shit a few years ago.
¯\_(ツ)_/¯
I think the declining attention spans link very closely to popular music, and I personally believe that the internet, for all its merits, has irrevocably damaged an entire generation. The fact that that Vine website became popular for hosting 7-second videos really indicates a fundamental problem with the youth, specifically their attention spans. It's possible for this to have also influenced music.
Prior to the internet, if you liked a song you heard on the radio, you had to go down to the record store and part with your hard earned cash for an expensive single or LP/cassette/CD; music had to be made to last, as less people would justify spending out on a single they'd only listen to for a couple of weeks. Therefore, the increased sales (and profits) from an increased sense of timelessness incentivised artists to innovate musically and work hard to produce the best music they could.
However, once the internet came about, people didn't need to leave their homes to obtain music; they could download it from the comfort of their own home without paying a penny.
I believe that, when something is paid for, it has more value to the consumer then if it were simply free. Of course, during the early 2000s when mp3 downloads were rampant, and even back to the 70s when music could be taped from the radio, artists continued to make music with long expiration dates in order to entice the consumer into paying money for their products.
However, now that artists can profiteer from instantaneous streaming services, they no longer have a requirement to 'sell' their music to the listener, as the listener need part with no money. They can simply pump out bland, homogeneous tripe and the listener will give them their required 'streams,' before totally forgetting about it and moving onto the next "masterpiece." As a result, the vast majority of this so-called music being produced today, particularly that which is aimed at young [& stupid] people, is cooked up with a very short expiration date. Of course, the artistry suffers as a direct result, but who needs creativity when you have flashy internet clicks?
