There are so many things he's doing wrong and I think all of them have been discussed in detail. So many things.
Take a recent example. He starts Welbeck and Walcott against Utd. Then he deploys tactics that nullify both. I'm reaching the stage where I wonder is it deliberate. How can you have Walcott up top and then (try to, because we didn't manage it) play a tight and short game in front of the opposition back four? Tip, tap, tip, tap, sideways, backwards, sloooooooow.
61% possession
You have Walcott wandering into the centre (and giving the ball away) just to get a touch. Walcott is good at one thing. Stretching defences with his pace. So when you see him running backwards towards OUR fucking goal to take a short pass and then lay it off BACKWARDS because the defender has easily tracked him you know there's a fool in charge. That ball should go over the top of that defender every time, with Walcott breezing past using his pace. Otherwise don't have him on the pitch because he can't do anything else.
Welbeck saves the fool's arse with a last minute header against Leicester. The guy is pumped. Ready for action. Back after a long layoff. Get him in the middle, don't stick him on the wing. Welbeck is good in the air, he has good tight control, he's unpredictable. Himself and Theo wide is a potentially dangerous combo. Or if you want to play Welbeck wide then play Bif too, straight down the middle. Be ambitious. 4-3-3 against a shite Utd team, why not?
4-6-0 tip-tap-tip-tap-tip-tap-backwards-sideways-hoof-lose it-scramble-concede-tip-tap-tip-tap-sideways-backwards...
You have to account for the opposition. When you beat the gypos and then get slaughtered by Soton all it means is your repetitive, unimaginative Plan A can sometimes work but is sometimes desperately exposed. And then there's the fact Wenger has no respect for teams he considers to be beneath him. He's always been like this, criticising and blaming teams with a tenth of his resources for defending, as if it is a crime. Every compliment he pays to smaller teams is double edged. "They were very spirited in defence, 10 men behind the ball!"