the fundamental theory of poker

does the theory not presuppose that the player last to act always has the ability to make the +ev play if he were to guess the hand of the player acting first? and doesnt that lead us to the assumption that the player first to act can never make the +ev play if the player in position knows his hand?

which leads to the conclusion according the theory that, if player A whom acts first is always 'losing' money if player B who has position can accurately put him on a hand?