You can’t protest the government as a concept nor any specific members of the top leadership. However, within reason you can call out localized corruption and give your input to local government initiatives.
Everything on the national level is beyond the scope of a normal citizens questioning.
Their seizing capital (including, IIRC, foreign-owned), cold war proxy bullshit, and domestic politics (a bunch of Cuban ex-capitalists ended up in Florida) are the reasons, I'm pretty sure.
All I saw was a suggestion that Cuba's political environment, including lack of sufficient democracy, can't explain the United States animus in general and sanctions in particular. Because we have much more accepting policies for a whole lot of countries that are worse.
Why pick this one moderately-bad actor to go metaphorically nuclear on when we're fine with everyone else? Hint: the answer is in Florida, not Cuba.