I don't think the problem lies in the backstory aspect. As I and others have pointed out, other games pull off entirely blank slate, no background PCs. The Pathfinder games both do it. The problem is that the narrative of the game doesn't really connect with the main character. The main character is a victim of circumstance, but so is every other player character. In Kingmaker, you're the leader. You're the one who takes charge of the party and leads, and because of that leadership you become duchess and eventually the monarch. The story is centered around you at all times. The conceit of the story requires you. Yet you can still literally be anyone from anywhere.
