Today the Secretary General has no power. Everybody knows that; along with the fact that he is also a puppet with the charisma of bucket half filled with sand. Guidance and executive power come first from the Central Committee; which I'm sure follows "tips" and "recommendations" from Raúl Castro (Fidel's brother), a man that should be effectively retired. Everybody knows that's not the case.
However, and being honest, I really don't care about labeling this place as a dictatorship or not (it is a fuzzy concept for me, and I won't fight hard for one or the other). Unless there's a clear definition, labels are sometimes subjective. Hell, this is not even a communist country, despite what they themselves like to present; this is not the dictatorship of the proletariat. And never was.