Thats part of it.
But more than ever music is a reflection of public tastes, and no one can accuse public tastes of becoming more nuanced and refined since the 60s.
I also believe its harder for innovation, Pet Sounds in 66 for example, possibly because of the corporatization of the industry.
Just my uninformed opinion.
I should say its harder for innovative music to reach a wider audience & so influence the direction of popular music...