The main theme that permeates all of Frank Herbert's work is that power corrupts and that governments and power structures are untrustworthy and faithless. The whole Dune novel series reinforces that messaging over and over again. The Fremen are portrayed as incredibly tough and independent because of the harsh environment they inhabit, and they gradually become less so as life gets easier for them.

The film largely held true to those themes and stayed true to Herbert's characters. Not so much with Liet Kynes, and that was a clear pander. Zendaya is not a good actor at all, and Chani is a redhead in the books, so that casting was also pandering, but casting Javier Bardem as Stilgar was actually a good choice, I think, and most of the rest of the casting was pretty good. The Atreides family was supposed to be of Mediterranean descent, so casting Oscar Isaac was not necessarily a "race-swap" as it's traditionally understood. The Harkonnens are supposed to be Nordic in origin, so Stellan Skarsgard was a good choice, and Dave Bautista's portrayal of Rabban is pretty true to the books, even though he's not Nordic.

My real concern is that they're never going to be able to maintain the faithfulness of those portrayals. A faithful portrayal of Vladimir Harkonnen would earn the film an R rating, for one thing, because in the books he is absolutely, disgustingly depraved. And as for what ends up happening to Paul Atreides' son, I don't think that will translate very well onto film, so if they end up making a film out of Children of Dune, they'll have to deviate from Herbert's vision while still trying to stay true to his message, and I doubt they will.