What you're failing to note is that the nature of the game itself has changed over the past decade or so. The main change has been the kickers; with training and practice techniques, they've just gotten better at hitting the long, GW field goal that prevents the other team from getting the ball. Combine that with the change in kickoff position to cut down on touchbacks, and if a team starts at the 35, they have to go about 30 yards to have a legitimate chance to win the game. That change has produced noticeable results in game outcomes.
For the raw data I'm borrowing from Peter King, who was a big advocate for this change.