Keeping the sanctions will only further allow the dictatorship and its sympathizers to explain away the regime’s own failings. It would be better for Cubans and the world to see the unraveling of Cuban communism without U.S. intervention.
There just isn't any intellectual defense of the embargo anymore. It is not the cause of Cuba's economic woes--Fidel Castro himself has said the economic model is broken--though it has made the lives of the average Cuban more difficult. It has not led to the ouster of the Castro regime. It represents limitation of the freedoms of U.S. citizens. It creates global sympathy for a small country perpetually bullied by Goliath.
None of these outcomes are good for the Cuban people, for U.S. national security or for the U.S. economy.