The big problem for Arsenal at the end was they only had one plan for defence, the press. If that fails they are in trouble.
Very good though their press is - it is probably better than ours, but if broken, it is disastrous.
The press also requires an intensity that is very difficult to maintain - especially at the business end of the season. Liverpool have suffered from this problem in tgmhe past as well and injuries have badly damaged it's function.
You need plans B and C as well And to transit from one plan to another in the same game.
City brutally exposed Arsenal's press twice in this respect.
At the Emerates City were under the cosh from the superb Arsenal press and City resorted to the targeted long ball up the field to Haaland to knock down to a midfielder OR long raking diaganal passes up field to wide players. The exposed rearguard resulted in Arsenal crumbling. Other teams have recently caused Arsenal problems with a more agricultural version of the long ball. The lesson is there though - the press can be broken.
At the Etihad, City played deeper than usual and simply passed round the press using withdrawn wide players with balls eventually down the channels to Haaland and KDB in the centre. Arsenal were enhilated.
The press is great but you need other plans that are less mentally tough to maintain.