Technically the UN was not created to be a police force, nor as a military body, it was meant to be a forum, a place where nations could talk out problems, plan actions and try to solve disputes with out the terrible cost of war. They don't actually have any real power, as such, they are a body that lets international consensus guide. The UN can declare and impose punishments like sanctions and trade embargoes, but it doesn't help if nations don't obey. Even more so it is a body that is meant to aid, not rage wars. Thats said, it is true that the world survived for a long time with out a peace keeper, but this is not really applicable any more, at least not with the power a nation can wield these days.....
Still, I don't think any one nation should be a police force, what I would like to see is full blown dissolving of nations and the creation of a true, progressive world state!!!! ✅