1. Big, big world, full of isolated cultures and vast wilderness. Travel is difficult and dangerous.
2. Player agency drives emergent story. Provide systems for play and development away from the table. Mechanical encouragement for players to maintain multiple characters.
3. Persistent environments that remember the accomplishments of PCs, and maintains the content that they generate organically through interaction with the setting.
4. Time passes meaningfully. Things change in organic ways, determined as much as possible by structures rather than DM fiat. The roll of years should be an additional play space, with systems requiring and rewarding down time.