You are just getting more experienced with music rather than just getting old. Mainstream music has always been fairly crap, at least for the past few decades. Its just now you are old enough to realise that fact, no doubt because along the way you've accidently listened to more alternative good music, and so now can distinguish the difference.
At the moment its autotuned club music, before that it was shitty R&B, before that the Britany Spears style pop divas and manufactured girl bands (Spice Girls, Bardo, etc), before that boy bands, before that whole wierd androgyny phase in the 90's, before that synth, etc. All crap, IMO.
Heaps of awesome music is made still, just don't expect to find it on commercial radio and MTV. You need to go out to small clubs with the local live bands and track down some small alternative radio stations to find it.
Alternative music is called alternative because it usually doesn't fall into currently defined genre, which means its something new and innovative. Sure, a lot of it will also be shit, but thats where good music is also found.
