A rich white dude who beats up the poor and the insane. ASPIRATIONAL!
Fun fact some-one who claims to be a professional economist on Tumblr actually basically buried this line of arguing about how Bruce Wayne being Batman doesn't help Gotham and he just runs round doing it to beat up poor people.
Basically Gotham is economically deprived and stays that was due to massive social issues way beyond the scope of what throwing money at it even for Bruce Wayne could solve.
The basic explanation is this
You have the dug in crime gangs.
You have the court of Owls who don't want things to change because they might lose some of their status.
You have the assorted wackos Gotham has attracted.
It means people don't want to live there so much because random wacko / gang/ terrorist / cult attacks happening. But also thanks to Wayne enterprises money there's good jobs going with good salaries and training perfect for people started out because your apartment will cost 1/3rd or less of your salary hell for 1/3 of your salary in Gotham you can get a mortgage on a house.
The issue is the gangs and wackos aren't going anywhere so once people are trained and have themselves mostly set up they can leverage their training and experience outside of Gotham to get jobs there
"Can you work under pressure?"
"Yes I'm from Gotham I had to get my work done while a gang of clowns tried to rob the place and a man in a bat costume fought them off"
and just like that talent and skills move out of Gotham because now they can and they no longer want to have to deal with random jungles sprouting up round town.
And thus they sell up and move and are replaced by some-one else with no-where else to really go looking to get a foothold somewhere.