Parity and over saturation are hurting the NFL. There are too many games on tv, and there aren't nearly enough dominant teams. Rules changes also hurt the ability to have dominant players. It wasn't long ago 3,000 yards for a QB was a damn good season. We also cared about who won the rushing title. Now, horrible QBs routinely throw for 300 yards a game and 3200 yards per season.
Approach 5 NFL fans then ask them to name the winners of the last two rushing titles. Many may be able to make solid educated guesses, but I doubt few will really "know". Monday Night Football was an event on its own. Now, there is Sunday Night Football, and very crappy Thursday Night Football. Not special any more. I also think Fantasy Football is hurting younger fan bases.
I have often said sports are built on a combination of 3 pillars:
1) Transcendent Players (Ruth, Ali, Jordan, Brown, etc)
2) Dynasties (Yankees, Niners, Cowboys, Steelers, Celtics, etc.)
3) Rivalries.
Parity and rules/policy changes have pretty much eliminated or stunted all three. Over saturation has hurt our ability to care.