Even if all N. Korea's nukes were taken out or failed, North Korea has thousands of artillery pieces, and the rocket assisted versions can easily reach Seoul, decimating the city. It is also reported they have tunnels under the DMZ they can drive military vehicles through onto the South Korean side. It's not as simple as just taking out military radar sites and bombing a few military sites like in Venezuela. While the West would likely prevail, there would be considerable loss of life on both sides, and while there are many bomb shelters under Seoul, the city would be severely damaged. And accordingly, China strongly supported both N. Korea and Vietnam during 2 past wars. Today's China with their world leading manufacturing ability is not a superpower you would want go to war against unless you can accept heavy losses. Whole US aircraft carriers of 5,000 men could be sunk with the huge, hypersonic "carrier killer" cruise missles DF-26 and the DF-21D of the Chinese.
We saw how NK materiel performed in Ukraine. Poorly.