It was always little more than a political statement made by scientists using their scientific respect in non-scientific contexts, a major negative. But they had some justification; the Cold War threat was that the two major superpowers would fling thousands upon thousands of highly-destructive warheads at each other, and anything that might conceivably be valuable in one of their proxies, which meant every major city in the world, quite a chunk of the merely medium-sized ones, and a whole whackload of "militarily-valuable targets" all over the place.

Let's be frank; if North Korea simply goes insane and launches everything it could conceivably have 5 years from now, it wouldn't even remotely resemble that outcome. At a civilizational scale, the millions of deaths, the square miles of uninhabitable land, the major disruption to international trade and unknowable potential changes in the international political landscape would still be a civilizational inconvenience, not the end of civilization. Even if it literally precipitated World War Three somehow, it would very likely still not even remotely reach the outcome that the doomsday clock was originally created to warn against. The Cold War legitimately threatened civilization as a whole, with a distinct possibility of human extinction.

To advance the clock in 2018 "because North Korea" is, in a sort of ironic backfiring way, an admission of just how far we have in fact come since the clock was started, because back in the 60s or 70s, the thought of advancing the clock because of this level of sabre rattling wouldn't have even crossed anyone's mind. This would just be Tuesday in the Cold War world.

(Similarly, advancing the clock because of "climate change" is another admission that the world has gotten much safer since the Cold War. "In 50-100 years, things might get civilizationally-inconvenient" is not the same threat as "Tomorrow, the human race may be on an irreversible course to extinction.")