Is this movie about a "satanic cult" like the description indicates?

It's a brujería-inspired cult, i.e. Caribbean black magic, similar to Voodoo. So it's technically not a satanic cult, as observed in "Rosemary's Baby" (1968) and "Race With the Devil" (1975), but you could still arguably describe it as satanic, sort of like Rob Zombie's "The Lords of Salem" (2012) equates witchcraft with satanism.

No, not at all. I thought the synopsis was rather misleading. The film focuses on voodoo, not a satanic cult.

It seemed like it was black magic of some kind. Sort of the Santeria version of what Satanists are to Christians. https://moviechat.org/tt0092632/The-Believers