If subject-matter learning can occur only after this initial game-mechanics learning occurs, how can educators justify the amount of time a learner must spend within the game just to get to the point where learning begins?

Game Play

It can take several hours of gameplay to learn the mechanics of some games and even longer for the more complex games. If subject-matter learning can occur only after this initial game-mechanics learning occurs, how can educators justify the amount of time a learner must spend within the game just to get to the point where learning begins?