Sir Winston Churchill famously said (1954) that: "To jaw-jaw is always better than to war-war." The UN is the world's top level "jaw jaw" place.
The problems, and here are many, that exist in he UN are minor compared to what it does.
First: don't forget hat the UN is much, much more than the gang in New York. Many of the UN"s member agencies, some over 100 years old, do excellent work on our collective behalf: think of the
International Telecommunications Union, the
World Health Organization, the
International Maritime Organization and the
World Intellectual Property Organization. All these agencies would exist even if there was no UN - some existed over 100 years ago before the UN, or even the League of Nations, was born. They, not the gang in New York do the real, day-b-day,
essential work of he UN. Consider, just for example, radio frequencies: radio waves do not recognize international boundaries so we
need some mechanism to
coordinate their use so that e.g. channels used for TV studio to transmitter links in Canada do not interfere with channels, in the same frequency band, used by public safety/first responders in the USA; equally, when you travel to Europe or Asia you want your mobile phone to work seamlessly - someone has to do the highly technical coordination work that ensures that will happen. The ITU does both: one of its output document, the ITU's
Radio Regulaions, for example, are under constant review and revision by dozens then hundreds and, every few years, thousands of technical experts from many of the ITU's 193 members and the document is a
treaty with the same weight in law as e.g. the Canad/US Free Trade Agreement, the Maastricht Treaty (which created the Euro (€) and the North Atlantic Treaty which binds us to NATO. You don't hear much about the ITU or WHO (unless there are fears of a global pandemic) but they ARE the UN in action and the long term consequences of their work actually matter more than the UNSC Resolution that
authorized our Afghanistan mission or the one that asked us to intervene, militarily, in Libya in 2011.
If the UN, imperfect as it is, didn't exist we would be busily inventing it. The Security Council is an anachronism, as was demonstrated nearly 65 years ago (3 Nov 50) when
United Nations General Assembly (UNGA) resolution 377 A, the
Uniting for Peace resolution, was adopted as a means of circumventing further Soviet vetoes during the course of the Korean War. Eventually it, the SC, will wither and die. The staffing of the UN, and many of its members agencies is wasteful, at best, often corrupt - but only a small handful of the UN's 193 member states are, themselves, anything other than inept and corrupt so we ought not to be surprised or even overly concerned when countries like Gabon, Russia and Saudi Arabia are 'elected' to e.g. the United Nations Commission on Human Rights and when UN agencies are staffed with highly paid nincompoops just because they 'represent' a region.
Doing away with the UN is a silly idea - it is far from ideal, but it is better than any alternative.