Could you elaborate on it being a "psychology problem" please? I agree with your perfectionism point; but how to test the hypothesis that it would be "fun"? A

Could you elaborate on it being a "psychology problem" please? I agree with your perfectionism point; but how to test the hypothesis that it would be "fun"? A rough prototype can easily not be fun, even if the hypothesis is true! User experience seems hard... Perhaps this is the reason for Mark Cerny's Method in game dev: to complete a slice of a AAA game to shippable standard, to tell if it's worth completing. Because players can't evaluate the experience of a game without the finished game. It's a hell of a lot of work, like $3 million; but doing just a slice makes it less than the $30 million for the whole game. Whereas, for some reason, for Zelda: Breath of the Wild, they developed a cheap 2D prototype to test out their "physics" and "chemistry" ideas. How were they able to test their hypothesis so cheaply? What makes a hypothesis cheap to test? Is it a bit like unit tests versus functional tests?