> If the only ingredient needed to support massive innovation and cost cutting is banning exports, wouldn't we have tons of examples of that happening already - like in Russia or Korea or Cuba?

That's just one of the ingredients that could help with chance of it happening, far from being "the only ingredient".

The other (imo even more crucial) ingredients are the actual engineering/research+economical+industrial production capabilities. And it just so happens that none of the countries you listed (Russia, DPRK, and Cuba) have that. That's not a dig at you, it is just really rare in general for a country to have all of those things available in place, and especially for an authoritarian country. Ironically, it feels like being an authoritarian country makes it more difficult to have all those pieces together, but if such a country already has those pieces, then being authoritarian imo only helps (as you can just employ the "shove it down everyone's throat until it reaches critical mass, improves, and succeeds" strategy).

However, it is important to remember that even with all those ingredients available on hand, all it means is that you have a non-zero chance at succeeding, not a guarantee of that happening.