That would be correct as in the novels (Fellowship, Twin Tower, Return of the King, and lore history Silmarillion) Sauron is mainly a moral philosophical concept (Catholic) than being a satan-like demi-god character.
He is talked about but rarely 'shown'. I do not think it is correct (Tolkien's intention) to portray him as an anti-hero or a type of humanoid villain from a point of view perspective like in a Sauron show. In a way he and the "Ring to rule them all" are the same thing, the concept of temptation for infinite and immoral greed & power.
This metaphysical force binds the story of the Ring together like a glue. So Sauron is in the books a type of backdrop with a backstory.
In the book Heart of Darkness (Conrad) and its related film Apocalypse Now (adaptation) the character of Kurtz is used in similar fashion to Sauron, as an overarching moral concept about Evil.