I do not think the main problem is that the HC does not provide the motivation an HC can provide (in many ways we have seen poor performance by the HC provide the motivation players need by being so bad they join together as a unit to protect themselves as was the case with Barry Switzer with the Boys and even a great tactician like Belicheck who (inadevertently unless he is smarter than I think) mishandle the Lawyer Milloy situation so badly the players came together under this jerk).
The problem is that there is not a core of seasoned and successful player leadership the motivates and leads each other in a refuse to lose attitude. For the Bills of old, this was a group of leaders like Kent Hull, Darryll Talley, Tasker, Thurman, Jimbo and even Bruce (who was no rah-rah motivator and was a very selfish person but he led by example of just being good and self-disciplined.
The HC is key as in the case of a delegator like Marv, but this team strikes me as missing an element that someone who has been there before like a Favre and someone who is just scary good like a Tony Gonsalez can bring. If one wants to fault Ralph for sitting on lots of cap room and not opening his wallet, one need look no further than this team deciding to go with Royal rather than paying the draft choice price for Gonzales and deciding to go with the benched Edwards and the FA Losman instead of Favre.