The Songbun caste system is the weakness that renders the North Korean society inherently unstable. The most able members of the society are discriminated against the most. And the more powerful and resource consuming "Core" members are not selected on the basis of merit. I think that there is historical precedent for the political principle that Aristocracy will eventually be replaced by meritocracy, but there may be revolutionary instability first.
It may appear that way to an outsider. North Korean defector, Yeonmi Park probably said it best. "In survival mode, there is no time to think about freedom."
It's so unstable that the existing government has been firmly in power for over 70 years, passed down from one generation of leaders to the next from just a single family with no present signs of slackening practical authority. If this is hoped-for instability, i'd hate to see a stable regime at work.
All the actions and effects you describe actually seem to make North Korean society more stable, at the cost of productivity, flexibility, and agility.
