Kim can't leave because he'll be tried in international court
That's probably the main reason the state is as it is. He can't open the country or it'll be easier for western agents to get him. He can't make the country freer or the people will rebel. The only option is for the country to become stricter, which takes more resources that the country doesn't have to spare, which makes civilian life even worse and which will lead to them falling apart.
If the elite turns against Kimmy, then it's a lot likelier that the country starts on the path to becoming free.
