Re: Sim can't form relationships at all despite interactions
@MinajSimmerr Ugh! It's terrible that the intro issue isn't fixed after all that. One friend did suggest that the sim could be corrupted somehow. Perhaps you could try saving the household to your library and then loading them in a mod-free save. When you save the household, they will keep all their money, skills, and levels when added to a new game but they won't keep inventory items or relationships outside of the household. It might be a good way to test if your save or your sim might be corrupted somehow, if your celebrity has the intro options in the new save. Before creating the new save, make sure all mods and mod-related folders are moved out of The Sims 4 folders. Also, you probably want to delete the localthumbcache file again.
As for those sims you mentioned ... there are certain features of that mod, when enabled, that create NPC sims to fill specific roles or may assign roles to existing sims. When the mod is removed, those roles no longer exist. I have no idea why they all show up at my sims' door like that though. However, it's possible that the game doesn't know what to do with these unfulfilled sims since their roles were removed, so they just spawn at your lot when loaded. I don't think it should have any impact on your game though. When it happens for me, they usually leave the lot fairly quickly. And, if you do create a new mod-free save, those roles (and rando NPCs) will never have existed.