Apples and oranges.  Regular entertainment programming (dramas, sitcoms, etc) has actually been shifting, not falling.  Shifting from traditional broadcast networks to cable, and in more recent years from both of those to streaming (Netflix, et al).

NFL games (with the exception of the Mon night ESPN game, a few Thu games/yr, and the expensive DirecTV Sunday Ticket for true diehards) mostly remain on broadcast TV.  The same shift in platform competition just doesn't exist for NFL games like it does for dramas and sitcoms.