Biggest criticism: We see three planets/settings in the movie - Atreides' planet, Arrakis, and wherever the Harkonnens live.
They all look like they were designed by the same set designer. Of course they were, but these are different civilizations from different species - they shouldn't all be cavernous but sparsely appointed rooms with some moderately ornate carvings sometimes but zero "adornments" of any sort. They didn't feel like they were truly lived-in by anyone, and were simply too similar to each other.
I've learned since I watched that the spice is needed to safely travel FTL because the navigators on the spaceships are all spiced up to see the future-ish/plan paths through space safely because of that. Now, I don't need an explainer on that super carefully, but the narration that spice is needed for space travel left me believing that it was a type of spaceship fuel. There's multiple scenes of space travel, just give me a few space pilots or whatever with blue glowing eyes or something.
Paul's mom is simply too young - now because they call her a concubine at one point I have to assume the Atreides clan does some sort of child bride shit, but that's probably not true? I thought the actress did an absolutely phenomenal job, both being maternal but also a fucking witch-freak at the same time, but the actress is only 12 years older than him and looks it.
The movie ends with a whimper. Obviously the book doesn't plan for a mid-point bang, but I've learned that basically there's going to be an intergalactic jihad in Paul's name in the future that he sees in his visions but is unable to stop. If you ask me, if you want to end this movie right, fresh off his first kill, bathed in the spice, give Paul one final dream of the future where the chaos that his hero's journey will lead becomes clearer. It doesn't have to be explicit but give us something to lust for - and something network execs who have yet to greenlight the 2nd film to want to realize.