I'm not an expert at this but it sounds like propaganda to me. Specially the part about Buena Vista. If they were not popular it was because peoples taste changed and probably considered their music outdated but music in Cuba has always evolved and continues to do so. Just because Cuban music has been blacklisted and not played in the US does not mean it hasn't evolved, most people just haven't paid attention.
I think there is more creativity in Cuba than most places as a matter of fact Buena Vista sounds nothing like modern Cuban popular music ( has the same base but sound is different). If it wasn't allowed to evolve it would all ways sound the same and thats your proof that it has. Jazz was still played (Irakere ) and even other American music such as rock and roll in the 70s. There are even heavy Metal bands, rap, reggae, etc in Cuba. Music, arts, sports, academics are all supported more than before Castro. Of course you had to meet certain criteria when considered for a spot at the music school such as being pro Castro which many people faked to get in. So yeah if you are openly against the government in Cuba then your chances of making it in music are almost non existent. But then again try being a supporter of Castro or communism in Miami and see how far you get.
I've been to many concerts of Cuban musicians a few years back and I never heard them push any political agenda or even mention anything about politics but currently the US government has denied them visas to come to the US and play. Also living there I met many people who believe in god and still practiced their religion maybe not as open as it is done here but they still did it without problems.
Another thing my father worked for the government like most people in Cuba and always told everyone that asked that he wasn't a communist and that one day he was moving here to the US to meet again with his parents. When he was offered to participate in political activities he refused and never had a problem.
Then again thats just my experience others have different stories I'm sure.
RIght now the biggest threat to Cuban music is reggaeton
and its not even American (based on Jamaican dancehall).