I wish sims had a whim to adopt a child. I just wish whims weren't being ignored right now and for them to update them. Since we have the ability to make sims that can't have children through more traditional means and the ability to have LGBT+ sims it just makes sense to me. Why put a feature in your game that is basically ignored by the sims themselves unless you actively tell them to do it? I bet a lot of sims players even forget adoption exists in game as well. If they can have the want to adopt a pet they should have the ability to want to adopt a child.
I also wish you were able to put a child up for adoption and for them, and children who have been taken away, to appear in the adoption options for another sim in town to adopt.