Hardest Part of Creating a Sim?

Going to the bother of making them look like they have a story and a personality, only to wind up having them be glassy-eyed lifeless hand puppets in Sims4, whose traits don't actually matter, for whom gameplay is a thin veneer easily scratched through and largely imagined instead of there waiting to be discovered. They may as well all look the same, because on the inside, they're all the same hollow puppets, really. At least there's still Sims3 and for those who live in countries where it is still supported, Sims2, for that good old gameplay satisfaction.