The Sims is unbearable without custom content and mods. There's a reason this community is so active, and it's not the Gurus dropping a barebones expansion on us every couple of months.
Just look at the gallery sometime, 99% of no-CC players only create Sims with the most recent content. Yeah, that'll be super exciting.
That alone is enough of a reason why multiplayer won't work; everybody's Sims will look the same, they'll have the same jobs, the same interactions... it's gonna be boring AF.
The dollhouse analogy is 100000000% true, though: nobody likes other people messing with their stories.