As for North Korea, the entire problem is that the mindset of the world is based on the reality of 15-20 years ago and has not changed to match current events. North Korea has won. It's got nukes, and it will never be undone. Reality trumps idealism. Further sanctions do nothing, and slowly trying to bring them into the international fold is the only long term solution. China, Vietnam, even Cuba have managed it. It's no coincidence that the PRC only replaced the RoC as the widely officially recognised China internationally after getting nukes, too.
Of course, defusing the Korean peninsula will be far harder. The only way of actually managing to do that would be to let the North annex the South, which ain't all that realistic. But if we can calm down Israel-Palestine, for the most part, we can do the same in Korea. If, and only if, we engage with BOTH of them.