I did not like the route/pattern designs. I am no expert, but to me it seemed that often there would be 2, and sometimes 3, Bills receivers downfield within a few yards of each other. Very poor "spacing". This resulted in a party of defenders also being in the area and that made for incompletions.
There were other things wrong, terrible o-line play e.g., but that is one area in which I was quite disappointed and felt was the OC's fault.