That hypothesis is, unfortunately, starkly false.
Music nowadays really is crap; time is not helping it. If we use our 20/20 hindsight and pick the best music of, say, the past 50 years, it will be heavily weighted toward the first 20 of those years.
Thirty years ago, sure, I thought that a lot of "music nowadays" was crap; but, unlike today, I also thought that a good deal of it wasn't.
OK...why do you think is it false? That you don't care about contemporary music doesn't really disprove it.