First, it looked like Stallworth struggled with the playbook and presnap adjustments. If this is the case, no matter what McDaniels did was not going to help other than dumb down the offense for a #3/4 WR. As to why he was demoted, you have no and I have no idea, but if it was because he didn't know the adjustments than McDaniels didn't misuse him.
Second, the Pats have done fine in the past with only one consistent deep threat or no deep threat at all. Never have we had a deep threat nearly as good as Moss. Moss getting double teamed means it opens things up for Welker and Gaffney in the short or intermediate routes. Why do we have to be so concerned about going vertical all the time.
Third, until you get a stat that shows all of Stallworth's dropped balls and passes thrown in his direction including the ones not on target, you don't have a solid basis to judge your theory. Say that 10 balls thrown in his direction were either off the mark or dropped and 8 of them were for over 20 yards, does your theory hold water.
Fourth, how many plays were designed to go to Stallworth deep and either Brady made an audible on the line, checked off him because he wasn't open, or just saw someone else he decided to go to someone else. All three happen all the time. None of them are McDaniels' fault.
You are basing your whole theory based on the number of catches Stallworth actually made over 20 yards, but you can't use only those to tell the whole story. Until you get more information, it is impossible to prove your theory.
As far as I am concerned, when a #3/4 WR gets 46 catches (27 for first down), 697 yards, and 3 TDs, you are doing something right. We did have one receiver have 98 catches for 1493 yards and 23 TDs and another have 112 catches for 1175 yards and 8 TDs. We had six receivers get 36 or more catches and four of them had 46 or more. I still don't see the problem with the passing offense.