I dunno, the UN was pretty instrumental in preventing the Cuban Missile Crisis from turning into WW3. So there’s that. Many have argued that the UN has been more effective at peacekeeping than, say, the US has. So it’s not a totally useless organization. More useful than their shortlived predecessor the League of Nations anyhow. I feel like the UN is kinda in-between a rock and a hard place:
If the UN stays out of most conflicts, they get accused of being useless and ineffective. If they stick their nose into every conflict, they get accused of imperialism.