Truth of the matter for the ratings decline is not very simple at all. It's multifaceted.
Deflate-gate - Went on for over a year and sucked-up NFL fan interest til the well went dry. In-Season to Off-Season to In-Season. For what?
Hall of Fame Game - The one that never happened. Fans are creatures of habit. Sure most HOF games are barely watchable, but we wait the entire off-season to get there. It's tradition...sheeezz. No season begins without it...until now. We deserve better and if the NFL doesn't find it's opening game to be important enough...than why should we be excited about anything following that 'bush' league garage?
Technology - We don't watch 'one' football game to it's duration in front of the tube in the living room anymore. Playstation, Ruko, Smart Phones, Sports Bars, PCs, etc. We watch as many games as we can while switching back-and-forth to avoid commercials and boredom during slow games.
Fantasy - Yes, the NFL did it to itself pushing it out there with multi-million dollar ad campaigns before once thinking, "How are we going to increase viewership when the fans have less interest in teams and more interest in individual stats?". That happened.
And last, but not least - This has been the most watched election cycle in history brandishing, obscenely record numbers of viewers. All other ratings outside of football have suffered equally.
That said, it has very little to do with any players. It has more to do with the under-performance of a multi-billion dollar conglomerate with very little foresight or intellectual fortitude to build their product and keep fans engaged while doing so. The NFL dropped the ball. Nobody else.