So why not extend that argument to WRs and RBs then?
If Emmitt Smith didn't have an awesome Oline blocking for him, he sucked balls (see his time in AZ).
If Randy Moss doesn't have a good QB throwing him the ball, he sucked balls (Oakland)
How far do you want to extend this argument?
Kurt Warner, as a Giant, was 5-4 with a QB rating of 86.5. Not great, but not ridiculously awful, either.