I disagree the UN's main functions are.
-Maintaining international peace and security,
-promoting human rights,
-helping social and economic development,
-providing humanitarian aid in cases of famine, natural disaster, and armed conflict.
Wars are still raging and we have a record number of refugees some of which have been in that state for over a decade. The UN has failed on it's own basic requirments.
Between countries.. in fact in many areas the UN is forbidden to meddle in the internal workings of a country unless asked to do so.
The conflicts we see today are not between countries, but between religions and tribes and internal in most countries.. it is also something that no one is prepared to deal with.
On top of that the UN does not have a military force of its own to actually do anything and requires the help of its member nations military, who all are very reluctant to allow their men to go fight in civil wars.. which I fully understand. Look at Bosnia. The UN/NATO only got involved and sent in troops in large numbers when the fighting sides agreed to a cease fire. Before that most countries were very reluctant to do anything but send in UN troops to maintain "safe zones" for civilians, and under extreme restricted rules.
If we want the UN or any other organisation to do something about things like Syria, or Iraq, or random African civil war, then you not only need the political will and mandate but the manpower and money.
Now all of this is damn hard to get. The political will regardless of the fine words coming out of London and Washington is not there. Why? Because like the Russians and Chinese and every other country, they want to make sure that giving any organisation the mandate to meddle in internal conflicts like a civil war, does not come back to bite them in the ass.
For example, had the UN had the mandate to do what you wanted to do, then the UN would have sent in troops to keep the peace in Northern Ireland.. would that have pleased you? Of course not. That is why most countries including the UK and US, would ultimately prevent a powerful organisation that could do things on its own to prevent/stop conflicts.. because it could be used against them.
Then there is manpower and money. The US refuses to put their troops under another country's command, so that leaves out the worlds most powerful military. Other countries have special rules on international missions, often put in place due to WW2.. thinking of Germany and Japan. And that leaves the bottom of the barrel basically with countries like Bangladesh, Nigeria and Pakistan contributing most troops... and those countries are where many of these conflicts are happening! On the money wise, it could be a bottomless pit.
I fully understand what you want, but it is just not realistic now and I doubt it will be any time soon.
