Obvious organizations like these won't be perfect, and there are a lot of flaws, and the UN has had its downsides every now and then. However the ultimate goal of the United Nations has always been rooted in good. The UN ensured that countries like England and Denmark would NEVER build empires. The UN has been a force for good, though there is much to be done.
The United Nations fails to accomplish a large number of its goals, and the extended massacre in Syria shows how ineffective it is at bringing crimes against humanity to a halt. With that said, dissolving the UN wouldn't make anything better, it can still be a platform for diplomacy and is well intended.