State of Decay has always only missed one thing, but it's the most important thing about a zombie apocalypse story, and that's deep relationships that make you care about each survivor they take out into the world.
Survivors should develop friendships, romance, or bitter hatred.
Friendships should result in reoccurring positive morale for the entire community. People like seeing people bond in friendship and it gives them a boost. If one of them dies, the other one slips into a deep depression (possibly resulting in suicide), fear (possibly resulting in fleeing the community).
Romantic relationships should result in reoccurring positive morale for the entire community as well. People will get a sense of normalsy seeing survivors comfortable enough to bond in that way in the apocalypse. If one of them dies, the other one slips into a deep depression (suicide watch), fear ( fleeing community), or anger/derangement (possibly resulting in arbitrary behavior i.e.; fighting fellow enclave members, or possibly murder).
Bitter hatred could result from a conflict of traits between survivors. This should result in a reoccurring negative morale impact. Bitter hatred to escalate to physical violence or even murder of fellow enclave members. This would be interesting because you may have two survivors you really need because of their skills, but you must make a decision to get rid of one. Also, there's a small chance they could reconcile based off of community conditions, seige survivals, or days survived. If one of them dies the conflict ends.