Why poker is hard
Chess and Go are perfect information games, both players see everything. The challenge is purely computational.
Poker is an imperfect information game. You can't see your opponent's cards. Every decision has to account for the full range of hands they might hold.
Standard minimax doesn't work. You can't evaluate a position without knowing your opponent's hand.
The solution is Nash equilibrium, a strategy where neither player can improve their EV by unilaterally changing what they do. In poker this is called GTO (Game-Theoretically Optimal). Unexploitable by definition.
