Sorry, a tangent, but I just had to speak up - part of my dual major deals with aspects of the music business and gives some insight as to both what labels/publishers and outside analysts have to say on that matter, along with several choice personal opinions from lecturers. Pop music has in general been shallow and repetitive since -forever-. What's causing the decline -now- honestly is the fact that policies, copyrights, distribution were all contrived in a period before digital distribution existed. A record was more of a physical product that you bought at a shop (thank you capitalism), rather than a service that you paid someone for (as it should be now, now that making a 'copy' of a piece of music costs a publisher literally close to nothing)
The music industry has taken years and years longer than it should have to realize this, clinging on to their old ways and crying foul (and suing 14 year old girls) while the rest of the world basically moved forward. If enough bigshots had realized the change earlier and stayed on top of it, digital sales would be way higher than it is, perhaps even more than the decline of CD/album sales. Look at some parts of the world, like Korea.