It’s beyond dispute that Kim Jong-un is a Stalinist, repressive political figure. Is he insane, as the US claims? Not likely, & certainly not more so than Trump. Is democratic social change necessary in North Korea? Of course, just as it is in most other countries. But that is for the people of North Korea to resolve.
If the US is forced to pull its nuclear & military forces & arsenal out of the region, the people of North & South Korea can decide their own political fates without US repression. They will likely, in their majority, decide to reunite into one country under democratic rule. What keeps the region at a boiling point is US military occupation.