so if I understand correctly, every person who has won a Nobel Prize for Economics has won a fake prize?

Yes. Any "theory" which makes assumptions falls apart if those assumptions are wrong. In game theory, the assumptions are, " It is assumed players within the game are rational and will strive to maximize their payoffs in the game." The equilibrium of Nash is that both parties will be satisfied. As you can imagine and having dealt with people daily, they are not all rational. In the law it is said that a settlement will leave both parties a little unhappy.

That last paragraph sums it up nicely and is persuasive.

“... the more we know, the more we know we do not know.”