I agree with @markmoskow ...I think '72 was great too. After than yeah, a long decline.  I mean, disco hit in the mid-70s, rock music had died by the mid-1980s, now it seems "popular" music is just a vehicle to sell singer branded merch and make them rich. It isn't even about the music. They become a "brand" that people want to associate themselves with...women buying handbags and perfumes with "Taylor" on them and all that. 

I mean listen to any average radio station today. It isn't the 1960s or 1970s anymore.  Different strokes for different folks.  I'm glad to have been able to take it all in from around 1965 till now and watch it (and hear it) zig and zag and change and move.  

But I think my interest in jazz (from all eras) is a reflection that rock is dead. 

@stuartk good points, especially about the "melodic and harmonic limitations". From around 1956 to 1976 we had 20 years of experimentation and creativity on display within those parameters. That’s 20 years of music. Today, much is simply derivative of stuff that has already been done. (The same can be said for much of TV programs and movies). Maybe we are just old and "been there, done that" so we look upon new tunes that are more of the same old, same old, "three chords and the truth" as not being up to snuff.

I love jam bands. Been seeing them since the Grateful Dead, but even there, it is becoming formulaic. You know when a up and coming popular jam band like Goose resorts to doing a version of a Justin Timberlake song we have come full circle.

Fortunately for all of us, there’s plenty of old and new music to be discovered. A few years ago, I "discovered" electronica and ambient music, when my experience was mostly limited to Kraftwerk, ELP, and maybe John Cage. Then we have all the great jazz records that you could spend a lifetime examining and loving.

What will music become going forward? No one really knows. Hopefully it will be more than just the soundtracks to video games.

But this body of work is out there, waiting for future generations to discover and love.  I believe some of them will stand the test of time just as classical compositions have after hundreds of years. If something is "good" I think it always will be.