The real problem.
Not to be too specific, sporadic to piss poor offensive line play. This is due to injury and lack of quality depth (common throughout the league.
This keeps us from having a consistent and effective running attack, which, combined with the poor pass protection, does not allow the QB (any QB) to function and leads to a poor offense, low points, low time of possession.
No number 1 receiver. If DVP had performed, this offense would be much more effective.
No pass rush complement to Robert Quinn, either from the DTs or the DE on the other side. Cam doesn't seem to be Cam anymore (I hope I'm wrong on this) and the light hasn't fully clicked on for Charles Harris (see DVP, but to a much lesser extent).
Combining the low time of possession of the offense with the aforementioned lack of pass rush (don't even get me started on injuries) is the opposite of a recipe for success. You need to possess the ball on offense if you don't want your defense to get gashed repeatedly in fourth quarters.
There are lesser problems as well, but the above are what is primarily derailing our season to date.