The Ivory Coast international has only shown glimpses of his talent since a club record £72million switch from Lille 18 months ago.
Pires told The Sun: “His game doesn't suit the intensity and demands of the Premier League.
“Pepe wasn't used to it and it has been complicated for him to change his mentality, to adapt to a new way of training and to settle in a tough league.
“I think he is simply not cut out for English football."
“We must not forget everything he did for this club and the quality he brought to the team.
“For me there is no culprit in this story. I know Arteta and I know Ozil. The manager made a decision and Ozil had to accept it, which he did.
“He never complained but instead continued to train like a professional.
“He has now found a solution to leave by signing with Fenerbahce and I think everyone's happy — especially Mesut because he was the one most affected by it.
“Being frozen out of the squad is very tough. That said, for me Ozil has already gone down as an Arsenal legend."