For the UN to intercede there has to be active support from it's members. Is Trump addressing the UN, No. Is Trump building a coalition of nations, No. Instead of building consensus, he's sending Pence and a naval task group to Korea and telling the world he'll act alone.
The sad fact is he probably has no other choice. He's made enemies out of China and Russia who hold two permanent seats on the Security Council and the only two countries that has any chance of influencing N.K.
The US had tried diplomacy for decades through several administrations. It fails every time because NK intends to strike the US as soon as it is possible. They have been very clear about their aims.
When someone shows you who he is, believe him.
The idea that we are rushing into something is ridiculous. Decades of negotiations and agreements have all been broken by NK. How exactly is that rushing?
Regarding the UN, the only entity responsible for handling this mess, they don't care. They aren't interested as you admit. Their only interest is bitching about Israel. Meanwhile, NK is still actively progressing in their mission to attack us. So, it is up to China or us.
We do not negotiate with North Korea. We do not have diplomatic relations with them and we don't recognize their sovereignty.
We should be using every once of our diplomacy to further isolate NK. The country has essential no oil production and produces less than half the coal they need. They also only produce about 2/3 of the grain they need. They need hard currency which they get from exports. Their major trading partners are China, Russia, India, Pakistan, Iran, and the Republic of the Congo. If Trump is such a great deal maker, this is where he should concentrate his efforts.
The US should be working through the UN to continue tighten sanctions and getting tough on countries that are breaking those sanction. Secondly, we need to be working through the UN to form a military coalition. It may not be needed, but it needs to be there.
Of course the biggest problem is China and Russia, NK's top allies. Our relations with China are problematical at best after a year of condemnation by Trump. According to Trump our relations with Russia are at an all time low after recent events in Syria.
Regardless of the long standing ties between China & NK, China's current economic relationship with the U.S. is far more important to them than their relationship with NK.
Whatever wingnuts may say about Obama, he put the screws to Russia and has set Trump up to negotiate with Russia from a VERY strong position. If we need Russia's cooperation in dealing with NK, Trump has more than a few cards in his hand.
Our issues with NK are of direct security concern for the U.S. Our issues with Russia are secondary. Trump should be able to negotiate Russia's cooperation without a problem.
In the end, NK leadership has put far too much emphasis on the importance of their nuclear program to the NK people. They will not be able to back down.
This leaves only a few possibilities:
1. War between NK & the U.S. China would possibly invade NK to prevent a total U.S. takeover and Korean reunification.
2. China forcing them to back down...possibly going to war with them.
3. Trump backing down and losing face. That will create the political atmosphere for impeachment.
4. Trump's spinning a state of continued pressure on NK, while NK continues to develop nukes, as a victory. Nothing really changes.