Why does the Real UN not work?

So with the way our Model UN happened on Friday, with the resolution passing despite objections from the developed countries because they were outnumbered by developing countries, i was wondering why doesnt that just happen in the real UN? there are way more developing countries than developed countries, so you would think that they would pass the resolutions that that will help the developing world, like the one we passed about financial aid and technology transfer. Does the US/GB/France/etc. have a veto like they do with the security council? or does the US just pressure everyone into not voting yes by threatening to cut trade opportunities or posing other economic threats? Why does it always seem like nothing happens when the world gets together to fix something?