Champ Bailey said:
I would say, without revealing too much, there is a revelation at the end of the movie that most people who haven't read the books might not have fully understood. You could definitely say that's on DV for not explaining better, but I think once you see the full story, you will come back to that last act and scene and find it more impactful.
But again, people shouldn't be expected to "come back to that last act" after ANOTHER movie to find the end of the first movie more impactful. I didn't have to see the The Two Towers to find the end of The Fellowship of the Ring impactful on first viewing. No matter how much something is a part of a greater whole, the parts should absolutely still be able to stand on their own. I'm not saying Dune: Part One ultimately doesn't, I'm just saying that in the moment people might feel cheated.