Lesser people would blame illegal downloading, but that is not the answer. The long and short of it is that the overall quality of music being produced is not up to par. Commercial radio is terrible, and has been for some time. However, I have found the listenability of it has been worse than ever. My job at the Wilderness allows me to listen to radio for a majority of the day and I can tell you, without a doubt, that the best and most appealing radio stations are those that play older music. My co-worker and I always gravitate to a classic rock station, an oldies station, and the old school hip-hop that is played at lunch time on a pop station. I have tried time and time again to listen to 94.1 WJJO, the Madison based current and new rock station. Each time my ears are subjected to the same sounding highly distorted crap. It's cookie-cutter rock, very formulaic and boring. Every song seems to be about suicidal angst that can only be identified with by teenagers who haven't discovered the joys of alcohol, or by 35+ year olds who enjoy alcohol a little too much. There are very few bands who actually display any above average playing ability (unfortunately it's mostly Disturbed and Slipknot who do,) the others all have the same song format and seem to use the same distortion sounds. It is not pleasant.
All hip-hop/rap is pretty terrible these days, too. It's all about parties, sex, and boats and hoes. Granted, I believe there is always a place for party music. The same goes for rock and roll. Most of Motley Crüe's tunes are about partying, girls, sex, drugs, and shouting at the proverbial devil, and that music is totally acceptable. However, when an entire genre of music, based on social change and innovative, expressive poetry turns into music that is no longer respected and is basically a joke, there's something very, very wrong. It makes me quite sad. (P.S. auto-tune is the worst thing to happen to music since Boy George.)
There seems to have been a pseudo-phenomenon with the band Owl City this past summer. A mostly "indie" band that has become quite large. The synth-pop style of music is one of the few genres that can be picked up by the mainstream crowd, MGMT is another example. It's weird, but it does make me wonder what would happen if the big radio stations picked up the music that is largely limited to college airwaves. This includes metal, rap, rock, and acoustic tom foolery. I'm thinking that things would change for the better by opening a new world of music to the mass public.
Now, I just want to briefly touch on one other thing. The fact that people can buy songs individually and not entire records might something to do with it. Artistically, it ruins the experience of the album, listening straight through from start to finish. For better or for worse, the album is being destroyed. I still believe that a single (and the the 30 second samples) can cause a person to buy an artist's full album, and that's what iTunes may have originally intended, but the music needs to be good for that to happen. Music industry...step it up. End of demo.