My point was that receivers have a hard time learning the system, as do RBs for that matter. This leads to players not playing a lot in the first and sometimes second year. Once the coaches do have confidence your susceptible to problems if the receiver and QB aren't reading the same things during the play. Don't believe that? Watch the game again, how many times do you see Eli make what looks like a bonehead throw with no receiver even close? Those are when Eli thought the receiver was going to do one thing, and the receiver did something else. The danger here is turnovers. It's a high risk high reward type system. Which is why you see one of the best offenses earlier in the year and arguably the worst in the past 3-4 games... and they are using the same personnel.
Hixon, Randall, Barden and Bennet have all had great games earlier in the season... so much so that they were being praised by even the most critical Giants fans. It's not all on Eli, and it isn't all on the receivers. Some of this is on the coaches who haven't made adjustments to address what defenses are doing, or to take advantage of the talent they have available to them. Your offense doesn't go from best to worst this quickly simply because of one thing... it's a lot of things.