You are right and I agree with many of your points. But two further ones need to be made to put them into context.
1. Every manager. Even the likes of Mourinho; SAF and Guardiola, make mistakes with their transfers; team set up and strategies. Manure; Citeh fans (let alone Spurs; Liverpool ones have made similar complaints against their managers this season. Wenger seems to be softer on his players than some other managers, but at the same time he has generally been better than his peers in unearthing unheralded gems - so I guess it evens up.
2. We tend to assume that another manager could take what Wenger has created and improve on it. I think that is a dangerous assumption. A new manager would come in warts and all, and if there was no silverware after a couple of seasons, there would be the same, or different, accusations to level. Sheer logic dictates that it with the competition that now exists financially in the EPL it will be a struggle for another manager to finish top 4, let alone win the league.