YC became valuable because of the ecosystem. YC enables so many varieties of exit options and inherently lowers the risk for the investors across various stages in the lifecycle of the startup company. If the only options are such that the companies have to become profitable in isolation or go IPO, starved off private capital otherwise then the risk is much higher. That’s why it may very well be impossible to create another YC that’s successful., unless you can replicate the entire ecosystem along with it.