I don’t know whether tourism is the solution here. Everyone in this thread is acting as if tourism means tourism from the US. The rest of the world is already free to visit Cuba and does.
Obviously the US is the juggernaut in the region, so tourism from it would turn the current Cuban tourism industry into mass tourism. And that would definitely inject money into the economy at the expense of social cohesion and nature. That’s not a good thing. Everywhere else in the world we’re trying to move away from mass tourism and the problems it brings.
The stupid embargo has to be lifted. That alone, being free to trade with the regional hegemon and those foreign companies the hegemon prevents from trading by threatening sanctions, would be enough to open up the economy. Sustainable tourism from the US is a part of that process, but not cruise ship hell.