How is that related? The QB has a plethora of receiving talent. Conversely, the WRs have no QB talent. WR's depend on the QB. QB's depend on the defense/special teams: starting position, offensive line, and receiving talent.
Essentially, claiming that Evans' drought is a product of his poor quarterbacking is unrelated to thinking that our quarterbacks are poor DESPITE having a poor supporting cast.
It's easy to say, "Hey you're making an excuse for Evans! Why aren't you making one for Edwards". The answer is quite simple. Evans has actually shown to be effective when properly utilized. With a decent quarterback (rookie season), and even as the top receiver (the next season), Evans has shown that he is a legitimate threat. If you want to look at stats, look at how many times he is thrown to. It's a depressing stat. A stat directly resulting from poor quarterbacking.
Trent Edwards on the other hand has not shown very much promise. He had a flash at the beginning of last year, but people like you built up excuses for him. Excuses that can't be proven with real stats like times thrown to.
In the end its an eye of the beholder thing, and you're very adamant on supporting players based on stats you make up (how many times a player makes a "long throw"? for example).