The job of the game engine is also to render the world given only the worlds properties (textures, geometries, physics rules, ...), and not given "training data that had to be supplied from an already written engine".
I'm guessing that the "This door requires a blue key" doesn't mean that the user can run around, the engine dreams up a blue key in some other corner of the map, and the user can then return to the door and the engine now opens the door? THAT would be impressive. It's interesting to think that all that would be required for that task to go from really hard to quite doable, would be that the door requiring the blue key is blue, and the UI showing some icon indicating the user possesses the blue key. Without that, it becomes (old) hidden state.
I'm guessing that the "This door requires a blue key" doesn't mean that the user can run around, the engine dreams up a blue key in some other corner of the map, and the user can then return to the door and the engine now opens the door? THAT would be impressive. It's interesting to think that all that would be required for that task to go from really hard to quite doable, would be that the door requiring the blue key is blue, and the UI showing some icon indicating the user possesses the blue key. Without that, it becomes (old) hidden state.