That was a major redesign. So was no man's sky, don't starve together, etc, etc. Whenever a game "adds multiplayer", they have to massively rework everything. The further you get into development, the harder it is to fit in.

Even Minecraft, which is famous for its servers, had to do parallel development for many years, with a completely different version between client minecraft and server minecraft.

That said, I suspect they are in the process of adding multiplayer support even at the moment, and it's probably one of the things slowing everything down. Still not a good sign though; we may be looking at 3-4 years before it's complete.

I'm probably not gonna buy the game till it is a game I want to buy, and for that it needs multiplayer.