That seems a bit harsh JC. I've watched games in which he certainly seems to lack motivation but there are several others on the team with the same problem. He didn't help his situation last week with his social media comments about China which isn't to say he doesn't have a right to his opinions, but stating them publicly like that is always going to have repercussions.
The game between the Gunners and Everton this morning was seriously poor. If I had to single out a useless Arsenal player I would point to Torreira. Too easy to knock off the ball and he inevitably ends up on the ground acting like he was shot. Martinelli isn't much better. Arteta has a huge job.