Comparing Arsenal with Man City will not yield a good balance because the two are not the same when it comes to the brilliance and consistency of their coaches. The weakness in Arsenal later got revealed due to a few injuries and all these still lead to the blame of the coach as that is part of what is expected of him to get the viable mains and backups. You also have a good observation that Alvarez and Foden are good backups for Man City, it is part of the plan. Even at that, Arsenal got relented months to the end of last season, they can't simply get it done with such unwilling morale shown.
comparing the two teams between Arsenal and Man City makes sense but saying Arsenal's performance failure and blaming the coach doesn't make much sense. if you can see as a whole this is not the coach's fault but have you seen the star players that are at Arsenal? maybe no.
well, that's the problem Arsenal need a star player who has high performance power like Man City has Haaland even though he wasn't too flashy in the champions league last season but for EPL matches Haaland has a strong performance.
so it doesn't make sense if you blame the Arsenal coach while it's not easy being Arteta who has tried to work hard to make a good contribution to bring Arsenal to runners up in the EPL.
Your points are not logical, maybe you should go back to read what you replied to for better understanding since it's obvious you just replied out of context. No one is entirely blaming Arteta, he tried last season and won awards, and no one is also disputing the fact that Man City has good firepower in their squad. What I agreed to in my response and agreement to a post by @BALIK is that as clubs are preparing for their main squad, they should also do so for their backups too, that's in case of the unforeseen. This one you are ranting by stating the obvious is what I simply don't understand.