If you look at the last couple of decades, the nature of what works and what doesnt in the NFL seems to drastically change every few years.  The NFL is very much a copycat league and teams evolve accordingly.  look at the last 5-6 seasons.  teams such as the colts, patriots, eagles (early on in that period) and others were succesful utilizing wide open spread offenses equipped with lots of speed and passing.  defenses around the league adapted accordingly and went to small quicker players who were better at blitzing/covering/stopping the pass.  now those smaller defenses are getting abused by the power running games of teams like the Titans, Giants, Panthers etc. The eagles offense just isnt equipped to play against modern defenses. 

with that being said the nature of NFL evolution is only a fraction of why our offense is terrible this year.  it doesnt matter what year it is, when you cant run the ball and your recievers cant get off the line of scrimmage your going to struggle