Seriously?
No one said Cooks "couldn't separate" I simply responded people were saying "our WR's couldn't separate WHEN HE WAS HERE"
Furthermore those images don't prove he was "Great" at separation. If anyting proves he had great hands (which we all agree on) and he can run away from people when he catches the ball.
Now find some Gifs of him getting stuffed repeatedly and taken out of games since you want to research.