My answer is ...
If a people deserve the government they have, the world is not ready for peace. The world cannot be united for a few reasons. 1. People want to fight; 2. People want to believe but disqualify others' beliefs; 3. People want to compete for pride that they are better than the rest - (nationalism is important for their pride); 4. People want to survive as they are with people, language and culture intact.
If UN cannot govern the world, are all UN's 'ambitions, declarations and ways of thinking' practical or 'only reasonable but not practical'?
This is an open question that I have no answer for now!
Does UN have all answers for current situations - religious wars, economic wars and all other human conflicts? I guess not! But why?
The reason is 'human nature'! People are just supposed to suffer by all means: our beliefs, our ways of life and our ways of educations. All these three things are based on gaining influence on others and gaining control of everything. These are to have everything for own use and not to let others share. These are to change others and to change the world. These are being lack of compromise and pleasure on others' sufferings.
'You are wrong and wrong no matter what and don't tell me why you're not wrong!' And all the wrong ones don't deserve peace! And don't want others get it right. Praying for others, without actual proper prayers, to fail.
But people don't really hate each other seriously... except for a few countries/peoples in direct contact though. Naturally people don't hate before they have known others. We don't hate the people we don't know exist. We start getting trouble only with who come into our scope of senses. Emotionally we need something naturally. If you didn't know my name, if you never saw my face before, if you never heard my voice … and if you never sensed my existence, your mind could not, yes naturally cannot, hate me. If you never read my writing, you'd never thought about what I had to say and you never care because you have nothing, just nothing to care.
If the UN could govern, the world would not need armies but only polices and never such fearsome weapons again and never had any such and such arm trades again. But the world likes FIGHTING, REVOLUTION, RELIGIOUS WAR, & CONTEST of STRENGTH.
The world is not made of just geniuses but Fake Geniuses as well!