I think you are underselling him a bit, and this is coming from someone who essentially share your opinion. He’s also positionally very sound, pretty strong in duel and has pretty good top speed which allows him to make the occasional marauding run from deep. However, my biggest criticism of him is his tendency to drop a good 10-15 yards more than he should when the other team has the ball, oftentimes even deeper than his CBs. That allows him to be in a great position for those last ditch tackles or interceptions but it also deprives the team of an option through the middle, when the guy who is supposed to receive and turn with the ball is in your own box. His sideway passing is also a direct result of this, because the pass to the CBs or fullbacks on either side of him is significantly safer when the middle is occupied by the AM/ST of the opponent in free space.
Arsenal fans are obviously very sensitive to any criticisms of his game, and often turn to accusations of rival fans being sour grapes, but frankly without him fixing that aspect of his game, I can’t take him seriously as a top midfielder, and that opinion has been held for years.