What is your favourite thing about the Sims 4?

I couldn't limit it to only a single detail, it is the combination of many (CAS, Toddlers, etc.). One thing I like a lot is the modularity in saving, like extracting a household and re-using it in another save. There is admittedly room for improvement (e.g. craftables losing their data between saves), but overall it allows to be very flexible.