Imagine apartments built into what used to be department stores, (Oh, you’re JC Penny 203? I’m at Sears 106). Get those old arcades up and running. Set up meal stations at the food court. Once people actually live there, stores will start to move back in.
If I’m unable to finish my life in my own home, that doesn’t sound like a terrible option.
Would be even better if instead of 2000 apartments, it was something like 1100 condos, then the rest split between offices, shops (including groceries), parks, and some sort of community recreation center. Do the same with the surrounding area, changing up the specialties of the locations a bit so that it’s worth it to leave your mall-sized area and visit others.
Then set up a mass transit system that goes between them, including consideration for people wanting to move large purchases like furniture and appliances, like one of the cars on the train has large doors, collapsible seats, and hardware for securing things too big for one person to safely hold. Or set up a parallel delivery system for things while the people ride the delivery system for people.
Then you don’t need the underground to go to parking and can increase the density of the area or put more space towards parks and recreation.
Welcome to many parts of Europe, you are invited to come visit any time :)