What foundation do you use to say that kids aren't good at music these days?
Katy Perry is a classically trained pianist who used to play in churches etc.; Justin Bieber taught himself the violin and piano when he was a preteen. I'm just thinking of two very popular artists that everyone likes to hate on these days; but there are hundreds of examples like that.
If a veteran LISP hacker said on HN "kids these days aren't good at computer science because all they do is write dumb web applications and iPhone apps", we'd all agree that it's a vapid hollow argument.
There's a difference between saying "Kids these days aren't "__ good at music __" and saying "Kids these days aren't playing "__ good music __".
The first is the OP's complaint and it feels new. The second is the complaint of generations.