I think they just need to completely overhaul the traits system as well as all the other systems they have implemented to have them work more cohesively together as well as have them matter much more.
The systems (sentiments, milestones, traits, lifestyles, etc.) as they currently are not inherently useless, but sometimes they overlap or don't make sense being together or even compete for attention. They really just need everything to work a lot better as I think if all these systems are properly implemented and combined Sims would feel a lot more lifelike.