By isolating his regime the blockade has actually insulated Cuba against the normal changes one might have expected through the sheer gravitational pull of a superior power up against a weaker neighbour. (Airto).

Which I strongly suspect has been the aim of the blockade. The economic blockade makes life harder for the Cubans, and it makes it harder for the Cuban government to relax the kind of restrictions that go with being a small country at war (cf Britain in 1940 on)(or, if you prefer, it makes it easier for the Cuban government to resist any pressures to relax the restrictions etc).

But the main target is outside Cuba. The blockade serves to warn other people from going down the Cuban road, by showing the terrible cost they will incur if they defy, anger and humiliate their big neighbour.