I think we cannot be entirely sure about the situation itself in Chosŏn. It isn't just propaganda what the Party says, it rarely reaches us (me at least) and on the other side what Western media says is also a distortion of reality as they try to demonize the regime.
It's far from paradise but would those people be happier with smart phones and coca cola?
Probably their country is lacking in things like clean water, food, healthcare and such, their isolation not entirely voluntary they are embargoed for a long time now.
There are things to build there, and not just infrastructure but their whole economy, they need something to join the world's market with. But they also lack of funding. I think while a peace would be nice there it's just complementary beside building up the economy as they could lower military spending and concentrate the resources elsewhere.
While he >>/17189/ mentions that's all about building casinos and hotels by Trump/USA the real business wouldn't be that, the real business - building up the economy - is already pocketed by China. But where will Choson get the money to pay the Chinese? From Chinese banks or the Chinese state which does (would do) the same here, finance construction work - for example - in foreign countries with one condition: these have to be done by Chinese companies.