As a millennial I can tell you that most millennials I know wouldn’t want this but instead make it a place for none corporation and community events and such. A public place where your not forced to buy things where can just exist with others even if you have zero money and accessible to all genders and disabilities and races.
And yes retrofit part of it for people who need to get back on there feet, and homeless people.
If we could retrofit them into homeless shelters we could but it would require rebuilding mostly everything as malls are designed for stores not housing people (for instance the bathrooms are not private and not easily accessible if you live somewhere in it)