Good discussion, guys.
I agree with pretty much everything you said, down to the 'lyrics don't matter' issue. I would focus more on the evolution of music from 1960-70, though - earth-shattering. That was a phenomenal period for music. There's been nothing like it, really, since then.
The early-mid 70s was more an extension and refinement of that. Don't forget to include FZ and Van Vliet in that mix, too.