It's odd to say, though, that the city needed to "out grow" Batman considering he'd only been working for less than a year which is hardly enough time to completely turn the crime-ridden hellhole that is Gotham into a city that could self-sustain its crime fighting procedures, especially considering corruption still existed in the police department.
I don't disagree with your analysis and it
is what I think they were going for but at the same time it doesn't make much sense in "reality," Gotham still, very much, had countless problems beyond what the local police department(s) and justice departments could do.