Also, this argument that "everyone has a boss" makes no sense. Yes, I have a boss, and he makes decisions. I make decisions too. Sometimes I disagree with his decisions, but he's my boss. The only decisions I can get in trouble for are those that I am tasked with making. Ireland wasn't tasked with making any decisions for all the years Parcells was in the building. It's merely convenient for your argument to say anything else, but, it is not backed up by common sense and life experience.
I should add, that your argument that a GM is tasked with simply getting talent doesn't add up either. So, under your theory, if a 3-4 defensive end is the top talent out there, then you should take him if you run a 4-3. Or, if the top talent is a 4-3 outside linebacker then you should take him even if you run a 3-4. Lets say your scheme calls for bigger possession wide recievers and the top player on the board is Tavion Austin, do you take him? I could go on and one, but the point is, it is well established that a GM has to acquire talent that fits within the scheme of the coach.