Could absence of coastline be a factor here?
Whilst Juche is, of course, a fiction even in the DPRK, is it a maintainable one to even your own population with no direct sea access at all?
The Donor Nation Aid you rely on may be disguised as normal imports, but the myth of Juche is utter self-reliance (to the point where it's almost a religious tenet) which falls down if you've no ports.
Closest landlocked comparison to DPRK I can think of is Zimbabwe, but that's still nowhere even near Juche-level.