he had a run of about 4 great months. after that time period, his game dropped off. hes been brought on to be "the closer" for us and normally when that has happened our entire shape and structure has fallen to pieces. during that stretch where we looked solid defensively, his work rate was immense and he did a great job positioning himself and winning the ball back. he hasnt done the same things since. he isn't a great reader of the game, his tackling technique is average, and he has very little range in his passing.
the latter point was papered over by putting cazorla next to him, because he could just win the ball and pass it 7 yards to santi, who would then dictate the play. hes not a box to box midfielder, he cant contribute in moving our attack forward.
i think people here lamenting his loss are just remembering his performance against man city and projecting that onto his performances since. he hasn't come close to that level in a long time.
the idea of playing with a DM is one i still subscribe to, in a 4-3-3 with the defensive midfielder as the pivot in the center. but in that role, we need someone who is big, strong, mobile and who can pass the ball forward and dictate play. i dont think coquelin ticks off any of those boxes, except maybe the mobile part. but a headless chicken at the center of our midfield is not what we need.