That's definitely part of the equation, but the blockade has been over for a long while. They have suffered not only the brutal effect of US colonization/hegemony but also the brutal effect of the legacy of Castro's brand of economics. If they were just suffering one or the other, they'd be significantly better off.

Edit since I am throttled on posts and cannot reply below: The US briefly blockaded Cuba in the 60s, but they have only embargoed them since then. They are not blocked from international trade by the US, except with the US. There is no meaningful block from Cuba engaging in the greater international non-US "global economy" such as EU,Asia, etc.