I think that game theory is really only useful in poker in the most basic situations, where the numbers are already given (e.g., in determing pot odds and things like that). But, for most decisions in this game, the numbers will not even be known, and therefore you will have to rely on your own intuition in order approximate just how likely you believe something to be. These situations include, the chances that your opponent is bluffing given past tendencies, the board cards, your pocket cards (as seen cards), and any other important information; the probability that your opponent is holding a certain kind of hand, given similar information. These are situations where you won't be presented with precise probabilities, but rather will have to approximate them for yourself using some crude form of intuitive statistics.

I feel that the crux of poker is not knowing numbers and doing math, because the numbers generally aren't even known, but instead it's on relying on your own rational judgement to decide for yourself just how likely something is.