Terraria
As I was discussing with a co-worker recently, Terraria is effectively defined by its multiplayer -- while Minecraft: Java Edition can function adequately (even preferentially) as a solo creative tool, Terraria is all about working together with your friends, and/or showing off your in-game accomplishments to them.
So with my pals having already moved on, so too have I lost interest in this. But while it lasted, and for the price tag, it was a good bit of fun.
Progress: Gave Up