A PC Warrior is a good combatant, but there are a lot of foes they can’t reasonably defeat. A PC Expert is superb at their chosen skills, but there’s no guarantee that those skills will be particularly relevant to the adventure’s challenges. Even the multifarious sorceries of the PC Mage are often awkward or unrelated to a problem. Instead, players are encouraged to think of ways around problems instead of going straight through them. If the tools your attributes and powers give you aren’t what the problem asks for, the players need to think of ways to make them what the problem needs. They need to change the terms of the situation to ones they can better handle, pull back to find a different route to their goal, or make a bet that what they’ve got will be enough in the end.
While this style of play can be challenging for many players, with solutions so often reliant on their own creativity and ability to shift the situation, it also has its special rewards. In Worlds Without Number, if your hero wins through to their goal, it wasn’t because you picked the right combination of classes or efficiently optimized your character build. It was because you, the player, made the right choices at the right times. You ran when you needed to run, fought when you had to fight, and trusted to your luck no more than you had to. Your victory is yours, and that’s a pleasure no dice-luck or forum build can grant.