There is a lot of Carribbean around to compare the place to, and frankly, it doesn't compare well to present day Cuba as far as quality of life for the average citizen.
As to your personal attack, I don't know... I don't really see anything wrong with enjoying visiting a place. Or with being nostalgic for what a place used to be. I also, for example, think it's a shame that Belltown in Seattle replaced its cool dive bars with trendy restaurants and condos. But it would be a bit silly to blame me for those dive bars having been there in the first place.
If you're worried about the visual appearance of Havana and, just pass NIMBY laws until you're satisfied they can't screw up the "neighborhood feel" too much. These are all solvable problems. Nothing here is reason to keep Cubans impoverished in exile from the world economy.
There already exists a city with rich Americans living in it, buying overpriced Cuban sandwiches from Cuban people. Using that as a handy comparison, I contend that the median Cuban in Havana currently lives a nicer life than the median Cuban in Miami.
They're going to exchange one for the other regardless of how either of us feel about it, because that's how progress always works. But my suspicion is that a few generations down the line the people concerned will regret it.
Have you considered asking them? Their answers might allow you to know their opinions, rather than presuming.