Nonsense, you had plenty of innovation. See, the Chiefs and Oilers would run on 3rd and long, and the Raiders would throw long on 1st and 2nd downs. Ok, so the 70s wasn't a good time for offensive innovation. But that is just because it was the defenses' turn to shine.
When I say I liked the NFL of the 70s better I'm not speaking of offensive schemes (although the modern paradigm for offensive innovation was forged in the 70s with Coryell) but of being a fan, of following a team.