Defenses have also changed, they are far faster, particularly at the LB and safety positions. teams are geared to stop the pass. I firmly believe a team that is designed from the top down to run the ball can do a lot of damage in this league. It's not sexy and the problem is trying to line up a great running attack with a great defense is really difficult. Even when teams seem to do it, it just takes one team that can take away the run to end the season.
Offensive styles are like fashion, nothing ever really dies. Hell, I was seeing ghosts of the triple option all over the NFL today.