It can't compete against capitalism when it's 90 miles away from the world's capitalist bully empire that imposes an embargo upon it and doesn't allow it to function. If I barricade you in your home and you become dysfunctional, is it your fault? No. The US controls the world's reserve currency and the international banking system. Thanks to coming out of WW2 unscathed, it became the world's manufacturing hub and primary, most prosperous economy, hence the world wants to trade with the US, not Cuba. If a country trades with Cuba, every cargo ship in its merchant fleet that anchors in a Cuban port will be barred from anchoring in American ports for six months. Who the hell is going to go near Cuba? No one, they've turned it into the economic leper of the Western hemisphere.,
You also conveniently ignored everything else I said in that post about National Socialist Germany which became the most prosperous economy in the world, in the 1930s, along with Soviet Russia. When the US and most of Western Europe were going through a horrible economic depression, Germany and the Soviets were doing well economically. It took world war, to change that. Even then, the Soviets got back on their feet and became a nuclear superpower despite the devastation of WW2 and not having access to America's "Marshal Plan" which helped Western Europe and Japan rebuild and get on their feet financially.
It wasn't until the Soviets, to stop the Cold War, tried to placate the US by becoming more capitalist-friendly, and due to an engineered Saudi Arabian oil price hike, that the Soviet Union experienced the worst economic recession in its history. The Soviets screwed up, by becoming weary of always being in a state of war, whether a hot-shooting war or cold war with the United States, they were exhausted and made some really bad decisions in the 1980s that led to the Soviet Union's dissolution. It wasn't a collapse but rather a betrayal and abandonment. Neglect led to the end of the USSR. They were tired of war.