The UN Security Council isn't meant to be a politically nimble engine for progressive economic change; it's meant to prevent a shooting war between those major powers. Judging the UNSC by the standard of that design intent and purpose, the UNSC has been quite effective, a few regional proxy wars could have been much worse for everybody on this planet. We can call it a failure if/when America and China start WW3 and cover everybody else in fallout, but that hasn't happened yet. So far, the United Nations Security Council is working well.