Whether he has the physical tools is only part of the issue. You have to have the head for it too. That's a large part of the equation and I think it's mostly what separates the bad from the good from the great. And that's the part Weeden clearly struggles with.
It's all well and good to be able to make all the throws and throw bullets, but you also have to understand your formations and read defenses and process information quickly and recognize disguised coverages and blitzes. And something Romo has mentioned that I think often gets short shrift, recognizing and processing spatial data.
In many ways the mental aspect is way more important. Yet people see guys with big arms and figure, well he has the tools to do it. And yes, you need a certain amount of arm talent. But we can't forget the brain talent too. And I don't think Weeden has that.