It's worth noting though that the shitty music of yesteryear doesn't persist in the public consciousness. When we think of music from previous generations, we're thinking about the stuff that was good enough to last (or bad enough, I suppose, if it's notably bad). So the popular music of today may seem to be dominated by shit, but you'd have to examine what else was on the airwaves of a given era to really make a good comparison.

I also think there's two major factors brought on by technological advancement and they both have a positive side. There are a lot more avenues to discover music than there have ever been. Musicians no longer have to be extremely talented and have broad appeal to reach an audience. From the listener's point of view, it's much easier to find good music that fits your particular tastes. And I think that in turn leaves more room in the mainstream avenues for lower quality but broadly appealing music.

The other factor is the accessibility of the technology to make and share music, which I think makes it easier for both "good" and "bad" music to find it's way outside of the artist's bedroom, so to speak.