It's not just music...everything's gotten worse.
I'm sure many will scoff at this, which I'm quite used to, but my pet theory is the "4th turning" thing. There are always talented and creative writers and musicians, but there are a lot more of them during an awakening cycle. And part of the equation is the audience as well...during those periods, all consciousness is raised, and there is more of a demand for authenticity, substance and meaning...so the "pop culture" in general elevates to higher level...a rising tide lifts all boats.
Some of those who are considered great artists are at least in part just lucky that they happened to be doing their thing during one of those cycles. It makes it much easier to be both artistically and commercially successful at the same time. The collective consciousness is more energized and at a higher "frequency"...so it makes it a lot easier for a talented, creative person to tap into it.
Most of the '60s and '70s were part of an awakening cycle, which IMO has a lot to do with the explosion of so much great music during those years...and why it has such longevity.