I don't think there are any remaining legal impediments to U.S. credit cards being accepted in Cuba. From my understanding, those impediments have now been lifted. The reason U.S. cards don't work appears to largely be a result of implementation issues. I agree with the basic premise that U.S. travelers should not expect their credit cards to work at the moment.
The issue of nomenclature is something I think is quite funny. Some people seem to think that U.S. travelers who say "I went to Cuba as a tourist" are misspeaking, because if they went legally they would have gone under one of the authorized categories. I'm thinking of the issue more generically -- the way one would describe the trip in nonbureaucrat-speak -- as an ordinary traveler. Those of us who want to travel as tourists to Cuba need to jump through some hoops -- yes -- but we don't need to let the U.S. government tell us how to think. That's what I object to. There's no need to be such slaves of irrational policies.
In any case, the first reports of the initial Miami-Havana cruise ship on May 2, 2016 suggest that travelers roamed through historic Havana at leisure with virtually no participation by anyone in so-called people-to-people exchanges.