I want to play a game like Fallout, with perhaps a light plot, but a much heavier settlement building mechanic.

Like, you found a settlement, and it’s filled with trash, debris, and burnt-out structures. As you scavenge and collect things, and attract people to your cause, the place slowly becomes cleaner and more structured. You can have settlers scavenge for themselves and fix up structures, farm for food, treat wounded, lead small armies against mutants and generally secure an area of a map, and really be able to treat the settlement as a home base.

Playing Fallout 4, I was bothered by how I could build out all these settlements, place structures and whatnot, help these people, and still no one had the sense to pick up a broom and sweep up the pile of trash in the street.