The United Nations may not be as effective as it could be, but it stands as a symbol for the unity the world's countries aspire to. What would be better is if the whole UN system could be looked at and revised so that it gets more power and can do its job better than ever before.
The primary reasons why the UN was instituted was to get every country involved in matters that have to do with human rights. As a result, many countries around the globe are benefit ting from the UN in multitude of ways. For example, when Iran chose to build nuclear weapons or has the intention to do so, every country gets involved because this is a serious matter.