You can say that about all or most managers, that a team wins or lose in spite of them because of the talent level on the field.
But there more to managing an MLB team then making in game decisions, yes as a first year manager he made some questionable decisions.. like I said above, what he has been able to do with a young and disfunction team, keeping them together and playing hard every game is a positive on his behalf.
The questionable in game decisions can improve as he gains experience, but handling a 25 man roster and keeping them playing hard when expectations are low is something you can either do or or cant do.. he shown he can handle it well, and especially in a media frenzy city like chicago.