I was looking at some, but there aren't too many that aren't just new outfits or skins to play with; at least on nexus.
Edit: they did a lot with Unity that I actually really liked. Between the co-op multiplayer missions/heists and story, you also had murder mysteries to help solve, and the "Paris Stories" (I actually quite like them. The Madame Tussaud ones are cool), on top of the assassin contracts. The gear customization was also probably my favorite of any other AC game aside from maybe Odyssey. I also kinda like the city events too, they let me roleplay a peacekeeper of the people type of character.
I haven't played Mirage or Shadows, but I wouldn't mind if they brought back some more "detective"/vigilante type stuff in the future.