Seriously. You need no additional evidence that Kubrick was a bat-shit insane genius than this film.
Anyone that says that describes it as “slow moving” is expecting entirely too many explosions for something set in the 18th century. Or they’re not paying attention. Every scene is dense with dialogue, imagery, narration, and plot-advancing actions. It’s complex (no fooling there) but not so complex that it becomes difficult to follow.
That said, you do need to be paying attention. And you do need to exhibit some patience to let all of the pieces come together.
Plus, the film is a technical masterpiece — even before you stop to consider the great pains to which Kubrick went to achieve all of those candle-lit shots without the aid of electric light.