The above is not true. It was not speaking to each other that caused world war 2. It was Mr. Chamberlain talking to Mr. Hitler and believing him that caused the problem.

It was also the League of Nations failing to live up to it's principles when Japan invaded Manchuria.

The UN was a dream to try and resolve things in a multi-laterial world, and sometimes early on was effective (See Korea). after the debacle of the Korean War (Moscow boycotting rather then using their veto), the progress in the cold war was almost always bilateral. (not always though).

In it's current form, it's useful - but I think the WTO / World Bank and the Red Hotlines have been far more useful.