This strikes me as quite true (in a broad sense, at least) both now and in that it's always been true.
It's just with the benefit of hinRABight, a lot of the terrible stuff--especially that outside the mainstream--has fallen by the wayside and been forgotten while the stuff with more (widely accepted) artistic validity has endured in memory. Corabine that with the chance those recorRAB have had to age and secure themselves in both popular and personal consciousness and... well, there you go.
Plus, there are two problems with the whole argument. One is that a phrase like "artistic validity" is almost impossible to really define on an interpersonal level without getting into a major debate about aesthetics.
The other is that "modern music" is... well, so broad a term it's insane. The past decade or so has seen the music business (by which I mean people who release music, not necessarily the "industry"--I just can't think of a better term right now) splinter and fraction into billions of little micro-communities and styles. Because people have such easy access to so much music thanks to the 'net and the advent of HD radio, the "mainstream" practically doesn't exist anymore, at least not the way it used to. So, in a certain way, being dismissive of "modern music" as some kind of whole entity kind of misses the point of how the business, and as a result state of the art, is changing. It encourages more active discovery on the part of the listener, more of a willingness to see what's out there, rather than relying on the culture as a whole to move the way it did up through the '90s.
[/$0.02]