They can, and do. Labour is actually one of the DPRK's main exports. They work abroad, and then return home. They mainly work in Russia and China, but also a lot in Africa especially for architectural endeavours.

Many of the defectors that live now in South Korea were tricked into leaving the DPRK, and now seek to return — but can't, because it's just as illegal to leave the RoK for the DPRK as vice-versa. A common story is one of visiting China, being approached by someone with a "lucrative opportunity" to work abroad, only to find themselves in South Korea, unable to go home. North Koreans are heavily discriminated against in South Korea, so they often end up homeless and underemployed; one of the only ways to make it big as a North Korean national in South Korea is to agree to conduct interviews and broadcasts for the anti-DPRK propaganda machine.

People who want to leave the DPRK can, but it's difficult and infrequent. There aren't channels that exist — on either the side of the DPRK state nor other nations — to assist immigration, on account of the sanctions on the country; only a handful of nations even have embassies with the DPRK. The exception is South Korea, for the aforementioned reason, and the two sides have a long history of kidnapping one another's civilians for political purposes.

There's also the fact that, well, people don't really want to leave. Despite the economic hardships, there is an intense sense of patriotism and nationalism that pervades every part of life in the DPRK. The desire to work as a collective to build the nation up even in the face of global enemies is hard-wired into practically every North Korean citizen, and the national spirit is one of happiness and unity through adversity, so it doesn't happen often that someone even wants to leave, let alone is willing to jump through all the hoops necessary to leave — or, more often, to take up the shady man's "lucrative" international offer.

I'm not, either. They're usually employed in Siberia, in logging camps, in Russia. In China they're factory and IT workers. Many monuments in Africa were designed and constructed by North Korean workers. You can look this up quite easily, it isn't hidden or controversial. VICE did a (really bad) documentary on Youtube on the former. BBC cites defectors claiming that North Korean workers were mistreated in China during covid lockdowns. Really, just Google, man. theculturetrip.com/africa/arti…

If you read about Juche and the philosophy behind it, you can understand their justification for the strong leadership and indoctrination. You can disagree with it all you want. You can disagree with economic theory, too, and Islam, and functionalism, and whatever other philosophy you like. But the fact of the matter is, you disagree with it because you have been indoctrinated with individualism for your entire life, just as they have not.

If you aren't a socialist, if you don't understand Marx's dialectics, or otherwise just think people should think first and foremost about the individual and class exploitation is a good thing, actually, you probably aren't about to understand the Juche idea. But if you are, and you're interested in developing your understanding of different socialist theories, you may want to read or listen to On the Juche Idea.

As Engels said, there is nothing more authoritarian than revolution. And the DPRK is actually extraordinarily democratic; just because there's a cult around the leader doesn't nullify that. The number of decisions are made directly by Kim Jong-un without any consultation is probably rather small, and they don't have anything like executive orders. They do, however, have regular meetings spanning all levels of government, right down to the hundreds of thousands of cell secretaries, who are elected by the ~200 people they represent each. Party membership is around 25% of the whole population. Both of these are unique in the world; no other nation, even socialist nations, have this level of integration between tiers of government.

The leader is an important symbolic position more than anything else. Kim Il-sung was likely inspired by religion, as his parents were missionaries, and he recognized how powerful the idea of an ideal figure for the masses to look up to could be. It isn't important that the figure has actual all-encompassing decision-making power, and indeed, as this figure is representative of the masses, it's important that he doesn't. What is most important, though, is that he represents the socialist ideal, a person by and for the masses, with a hatred of imperialism and a love of all people, nationalist and internationalist, selfless and hard-working. And, well, it appears to work: You can call it brainwashing or indoctrination or whatever you like, but the fact of the matter is, it has produced an unshakable collectivist culture and, despite all its hardships, possibly the most stable society on the planet, with very few and small visible prisons and police. If you oppose this, it has to be your gut reaction to an ambiguous "authoritarianism", a feeling of distaste for a figure that appears cultlike to you, rather than anything material.