The problem is that Will Wright is a programming genius. His genius was in building a Sims personality thru a handful of common traits. Shy/Outgoing, Lazy/Active, Grouchy/Nice, Sloppy/Neat, Lazy/Active. When you combine these handful of traits they spawn a limitless number of behaviors and what appears to be true AI. "Traits" from Sims 3 and 4 are just silly and nonsensical. Honestly they feel lazy and their effects limited directly to a specific activity instead of being dynamic like Will Wrights original system.
Ideally Maxis should bring back the Zodiac based personality system, and then allow players to choose traits to modify that base personality. Then they could weight activities and objects based on those personality traits. For instance a television would have a stronger draw for less active or playful sims. In conversation a playful Sim would be more likely to tell jokes, and a grouchy Sim more likely to react negatively. On top of that you'd have the modern idea of traits like "nerd", "Snobby", or "Loner", but much like the personality they would function in a more dynamic way with weighted objects and behavior.
I could go on forever, but simply put it'd be really easy to create truly dynamic Sims without even applying much effort if Maxis just actually looked back at Will Wrights original work and learned why it was so amazing to begin with.