If Cubans had just been allowed to freely trade with the U.S. the Castro would have been memories within the space of a few years. Instead, sixty years of sanctions have locked Cuba into a early 1960s time warp and Cuba remains defiantly Cuba. From Kyle Anzalone and Will Porter at libertarianinstitute.org:

Sanctions have quickly become the foreign policy establishment’s favorite tool. Blacklisting governments opposed to the empire’s agenda allows for politicians to look tough on ‘evil regimes’ while stopping short of the type of warfare that is largely opposed by the American people.
US leaders present sanctions as a low-cost option to punish bad actors and give oppressed people a chance to rise up. However, the results are almost always the opposite.
The Cuban embargo presents the best empirical evidence of the failure of sanctions. Though the blockade just celebrated its 60th anniversary, the Castro government remains in power, serving only to increase the country’s poverty, not its freedom. While Joe Biden campaigned on rolling back the Donald Trump-era restrictions on trade and travel to Cuba, he has so far failed to live up to that promise and is likely to pass the blockade onto his successor.
Further, Cuba presents a perfect example of the hypocritical demands Washington attaches to its sanctions. As the US says Cuba must free its people to access the world economy, it continues to run a lawless torture prison on the island, largely filled with innocent Muslims.
Since the Kennedy presidency, sanctions have been wielded against a long list of countries. The US is currently waging ‘maximum pressure’ campaigns against Iran, Venezuela, North Korea, and Syria, a blockade against Yemen and Cuba, a trade war with China, and additional penalties on various people in Russia, Asia, the Middle East, Latin America, and Africa for assorted infractions of the US-enforced “rules-based international order.” Those policies have seldom had the intended result.