Cuba's future will not be resolved in Rome, or even on the streets of Havana. There is no future for this island separate from what the United States will approve or tolerate. This may not be a happy fact, but it is a geopolitical one. Cuba has more to come to terms with in Miami than in St Peter's Square.
The Pope's excuse could be that he is enjoined by the Gospels and his stewardship of Peter's keys to welcome them all to the Vatican. But what is Fidel Castro's rationale for climbing the steps of St Peter's in order to smell the smoke of the people's opium? It is surely a bit late for priestly intercession for reprobate revolutionaries.