Indeed, creating an mmo (even if all assets are available) is very time consuming and most people underestimate all of this. I've started with UE too, but decided engines like UE and Unity are not the best choices for a MMO.
Edit:
We are still working on it. 2 focus on the worlds, while I work on the code.
As soon as I finish the character selection, creation & deletion (basic design), I will move on to the world and work on the object spawn, movement and everything else. Then more progress will be posted.