For the rest of the world the concept of working together and having a chat before going to WWIII seems worthwhile.
Agree with the desire for peace, but it doesn't logically follow that in order for governments (or more accurately, superpowers) to have emergency conversations, the world requires a standing bureaucracy headquartered in NYC. The existing worldwide network of embassies and foreign service personnel are perfectly capable of scheduling multilateral conversations on demand.
Empirically, also note that the closest risk of WWIII in the past 50 years, the Cuban missile crisis, was not resolved through the UN, but through direct diplomatic channels between the USA and USSR. Everything the UN does, can be done ad-hoc or by other organizations.
Even if you disagree with my points, how about a compromise? Move UN headquarters from swanky and desirable NYC to somewhere less pleasant but more relevant, like the middle east or Africa. Then, we will see how many UN representatives are truly committed to the causes they espouse, or whether they suddenly decide to make a change in careers.
