dynamic choices
let the game make the mistake.
Everyone who has played Dark Souls knows the feeling. You swing at the wrong moment, hit an NPC you needed, and now they're hostile or dead, and whatever quest or item they were holding is gone for the rest of that playthrough.
That dread is a big part of why so many people play with a guide open. When a game is linear and every outcome is fixed, there's a right way to play it, and the only way to avoid a mistake is to look up the answer first.
The idea I keep coming back to is taking that fixed path away. Put a clone in the world, a doppelganger of the player with its own intentions, and let it make choices too. Say the evil clone decides to kill an NPC you needed. In most games that would be a disaster. In a game built for it, that's just where your story goes next.
The min-maxers will still chart out every scenario on a forum. They always do. But if the clone, the economy, the resources, and the relationships between characters all react to what happens, no two playthroughs will be quite the same, and there's no single right answer to look up. There isn't really a better or worse path either, just different ones.
Somebody will always feel like they got the harder game. That only holds up if they're comparing their run to someone else's, and even then there are so many variables that nobody can say for sure who had it worse. At that point winning matters less than the story you ended up with.
That's the kind of game I want to make: one where the world keeps moving whether you get everything right or not, and a mistake is something that happened to you instead of something you did wrong.