I mean, it's a novel about the politics of foreign powers trying to extract a valuable resource which is crucial for transportation from a desert region that is explicitly described as looking like a cross between Mexico and the Arabian Peninsula (even to the point of Arakis having date palms and saguaro cactus), so uh...
...what was a turn off? That the author felt the need to point out the glaringly obvious?
(Obviously the book explored many other themes about power, religion, culture, environmentalism, etc., plus it was a pretty good story. But you can't really pretend the Middle East and oil weren't also major themes in the book.)