I've got no mods or other downloads at all, and free will on high, and my sims both interact, take care of their needs and so on.
I do recognize this from sims 2, where this could be a sign of conflicting mods, so that could be the problem

You might also have to turn on story progression. I personally, like to have that one off
(honestly, I've never played with it on).
And I'm not so sure they'll do romantic stuff on their own, at least not in the active family. I've not seen any of mine do that.
Then again, they're more busy doing other things, and the only adults on the lot I'm playing, are married.