I just wanted to offer some advice on the main essay topic as I know some people are racking their brain over this. Oxford wants to learn about your values. If it is shocking to you then it’s probably tripping upon some deeply felt principal. Ponder what that might be and speak from that place. Consider that they are trying to get to know you at the deepest level by understanding what motivates you, and examining if those values are a match for the Oxford Community. To generate some ideas you might actually consider looking at successful essays for Stanford’s main essay question which also speaks to values. For the part about how you would change this, I think they are looking to assess your innovative and strategic thinking abilities. Be imaginative.