I was thinking of his other works like BuSab, Void.

For Dune, there is a very complex world, but the reader only gets the minimum necessary exposure to it. There's no explanation for how the major powers came about, they just are, ditto for what the Holtzman filed/effect is, how a no-ship works, etc. There's no history/explanation of what the Butlerian Jihad was, just it's long term effects.

Don't get me wrong, I love his style of storytelling, Dune is my all time favorite series of books. That why I listed him in a list of the best.