It goes hand-in-hand with the decline of major-label money: The quantity of popular rap music in the charts has seen a marked decline due to the rise of The Armchair Internet A&R. The result? Arguably, the proportional decline in the quality of popular rap overall.
There was a time when an A&R rep had to be a knowledgeable talent scout, scouring hip-hop scenes across the country for the most successful artists. Today, A&Rs are the bloggers digging through emails, creating headlines through word-of-mouth viral buzz. The importance of being able to create Internet headlines means that the music industry is, more than ever, relying on a strange subset of people (who spend a lot of time online) to decide what is or isn't buzzworthy (making decisions on which they stake their own reputations).
Less important than "will it appeal to teens?" is "will it appeal to teens online?' Internet noise is now one of the most significant drivers of content for the chattering classes.
Herein lies the strange contradiction: Sure, A&Ring has been democratized across the board; anyone can "discover" an artist by blogging about them first, leading to a viral falling-dominoes effect and kick-starting a major-label career. But what interests those dominoes—the Tumblr rebloggers, the music critics, the magazine editors—isn't necessarily what interests the wider public.
For years, what music writers have covered and what's been popular with music fans has diverged significantly. Now the pool of writers (or rebloggers, at any rate) is expanding, but it remains non-representative of the wider world. We end up with rap artists who would have only been critical darlings less than half a decade ago receiving all kinds of hype and attention.