I think Fortnite is the opposite, its designed by rapid iteration and prototyping. Epic had almost a decade to develop this game - and others - and iterate on them while they were financially supported by external investment and the success of Unreal Engine. It paid off when they finally found the right combination; skilled developers, excellent tech, accessible artstyle, free to play, battle royale, and construction. The only other studios that can really accomplish something like this are Blizzard and Valve.