Well, you believe is ineffective because you've been listening to the left for way too long. The embargo was never intended to bring down Castro, US foreign policy towards Cuba has been one of containment...by restricting his access to dollars/credit and/or US markets, Fidel's economy has collapsed, and the collapse of the Cuban economy helped bring about the collapse of the USSR's economy as well, Cuba was a bottomless pit for Soviet rubbles. This embargo that you deem ineffective helped bring down the Soviet Union as a side result.
Fidel's plan, from the very start, was the expansion of communism/totalitarianism in this hemisphere, the US embargo, and the Cuban government's innability to access funds from the World Bank severely limited Castro's dreams of exporting his "revolution" to Central and South America. He still did it, at the expense of the welfare of the people of Cuba, but nowhere near as widely as he had hoped for.
The embargo has kept Fidel busy shoring up Cuba's economy for four decades, not giving him time for much else.
Souns like a resounding success to me.
ok, so now that all that is in the distant past (no more ussr, no more exporting of communism within our hemisphere), WHY DO WE STILL HAVE AN EMBARGO????