Unai Emery has a mad difficult job on his hands, he has a squad that perhaps only Wenger can optimise their performance.

Similar to when folks criticised SAF for leaving Moyes a poor squad, it wasn't a "poor" squad, just not a good one for Moyes

The player profiles at Arsenal at not naturally synergistic, there is no real balance to the squad, probably too many options of style that they can utilise but in this case it's a disadvantage because it's not clear which the best one is

Emery probably has to eventually axe 1 or 2 big players for the sake of the team.

One or two of Ozil, Ramsey and Xhaka probably need to be dropped for the team's performance to be optimised. Big calls for any manager to make

That being said, there's reason to be optimistic. They caused loads of problems for Chelsea in that dominant 20-25 minutes spell that ended the first half.
Also in my experience, games such as ManCity and Chelsea accelerate the development of a team