If you look at the weapons Brady had before Welker, there wasn't much there. That's not arguable. He's never had a running game. Troy Brown was a nice player, at best, a top 15 WR. Aside from him, there wasn't much. I respected Brady for being able to do the things he could do (like win 3 Super Bowls) with the few weapons he had.
Yes, his numbers get better when you add talent. Welker and Moss helped, they had a record-setting season together. Having Gronk and Hernandez help. But when I look at Peyton, Eli last year, Rodgers, Brees, etc, I see more talent to help the QB on those teams than I see in most seasons with Brady.