Is The UN Working?

I can't decide if the United Nations is working or not, whether it needs to be scrapped and started again or left as it is.
We presently have five nations having a veto who can scrap anything the other 192 countries decide should happen and that is surely not very democratic, one country able to defy the will of all the others.
As with Russia who will defend its friend Syria, we have America who will hear no criticism of Israel and as we are seeing now and in the recent past with Iraq, if a country wants a war and the United Nations say no, they just ignore it anyway. 
The last 67 years of United Nations existence has just been the big five, UK, USA, Russia, China and France, pursuing their own interests. The Russians have thrown down its veto 123 times, the US 83, UK 43, France 18 and the Chinese have wielded their veto 6 times.
With the exception of Israel, the United States and United Kingdom have probably been the greatest warmongers of the past 60 years as well as the greatest arms exporters but somehow are they are most responsible for upholding global peace.
But now, as the veto powers of two permanent members (Russia and China) obstruct its attempt to pour petrol on another Middle Eastern fire, the US, UK and France are worried about the future of the United Nations because they object to the fact that it is working as it was planned to, with two nations able to pull the rug out from under their plans to do what they want.
That's where my confusion comes in, during the build up to Iraq, permanent member France whipped out the veto and stopped the US and UK the fig leaf of legitimacy and although they went ahead and invaded anyway, it did not have UN backing and was illegal.
Now China and Russia are standing in the way of Obama's, Cameron's and Hollande's plans and if they satisfy that itch and go and strike at Syria anyway, again it is illegal as it has no UN backing.
Therefore, the UN is doing its job, stopping aggression and making any subsequent military action therefore illegal.
The problem seems to be that once the UN has been defied, there is no sanction against the countries attacking another one without the UN say-so so the problem isn't with the United Nations but the lack of punishment for defying it.