"Some brilliance, somewhere, was going to be expressed, and now it won't..."
It would seem to me that great artists create brilliant works because of his or her love for the craft. ("Well I know it sounds funny
But I'm not in it for the money, no...") Think of the many writers, playwrights, composers, etc. that made very little money off of their masterpieces. Even artists today may write some of their best music at a point at which they don't necessarily expect riches from it.
To say that it died only because Napster or other services arrived on the scene in the late 90's seems something of a tortured argument. The more unpleasant possibility is that the Top 40 is the Top 40 because that is what a certain demographic wants or, at least, accepts. Music's prior shifts in taste (or simply industry promotion and output) were not likely "natural" either. There is always a segment that appreciates good music though and that music may be rediscovered in the future.
Anyways, I think the explanation is more complicated than what Gene said. Obviously, those silly music game ("reality") shows don't help. I find it impossible to suffer through most of what is blasted through television or radio currently, but I have always been a bit different! That's my devil's advocacy for today.