It is still illegal for American citizens to go to Cuba but the exception of family contact and for US government approved education and cultural exchange programs. But tourism is thriving in the country, with Europeans, Asians and other regions of the world going in ever increasing numbers. There are hotels and tourism development, and lots of outside investment.
The policy of the embargo by the US is looked at as childish by almost all the world, it is not working whatever the goal is, the only place from which there is not trade, tourism and investment is 90 miles to the north.
Despite the prison sentence awaiting Americans going on their own if discovered, or owning a Cuban cigar, thousands of visitors from the US do go anyway. Flights are daily from Central America, just go. Arriving in Cuba with a US passport, your passport will be entered but not stamped as entering Cuba. A stamp is affixed to a separate paper that is advised to be destroyed before entering the US.
I am a US citizen living in St Petersburg Russia and see that many of my friends here have visited since it was a popular resort region during the Soviet era when flights were dirt cheap. After the independence of Russia from the Soviet Union, the new Russian Federation did not subsidize flights there or even offer foreign aid. Travel to Cuba by Russians almost stopped but in the last 8 years or so it has become popular with young people to visit, but flights are not cheap anymore.
Cruise ships stop there now but they probably do not accept US passengers because there would be a positive record of the passenger entering Cuban waters.
If someone wants to go using the people to people education programs, which tend to be pricy they can contact Semester at Sea or Road Scholar, both of which conduct legal tours.