>random background npc mogs entire named cast of game and (you)r V
>many such cases

Each faction needed a handful of interactable NPCs with short side quests/romances. Even just 1 guy and 1 girl per gang with a platonic/romantic quest chain and come to my house interactability would have them sitting comfortably at skyrim numbers. Seems modders tried but just don't have the tools or VA access to fill these gaps in world fidelity. Outside the Rita wheeler mod and Lizzie's BrainDances there really isn't anything else (for 2.21) that flushes out night city.