Similar story here. For me what killed my enjoyment of it was the developer teasing and announcing Unturned 4.x but taking so long to polish it, that Unturned 3.x got abandoned.
He's come back to Unturned 3.x since I stopped playing, but the fun's no longer there for me anymore. I enjoyed the crap out of the arena gamemode and the creative servers (I basically played it more like a sandbox than a survival PVP game) but neither really have players anymore.