It's not that simple. The game is about overcoming obstacles via means at your disposal. It is unfair to expect players to suddenly switch from that mode to adventure moderation mode. If the characters have win button, it makes sense for them to use it, even if it makes a duller game. If Gandalf would have had an ability to teleport the ring into Mount Doom, it would not make sense in-character to not to do it, even if it would have resulted a boring story. The solution is to not give characters such a win button in the first place.