The people just aren’t up for it. And when you don’t have the people behind you, you’ll get couped if not straight up murdered trying to do something like that.
It’s easy to get a warped view from the comforts of Western internet left that fetishizes the DPRK and Cuba, but let me tell you that very very few people even in poor Global South countries want to live like that. They’d rather believe that working hard to sell cheap goods to foreigners can at least earn them some treats in return, than to completely upend their entire lives and being confined to material poverty like in Cuba or the DPRK. You need people to be ideologically committed to your program and willing to endure the economic hardships that come with it.
This is why people took the risk to cross borders illegally because they believe that the such risks and the hardships that accompanied the arduous journey are worth more than staying where they are with little hope to offer in economic and material terms.