People already have a lesson from following personality cults in Adolf Hitler. No, life isn't all happiness. That's the reason movies should be an escape from unhappiness. Through Paul and Chani viewers can feel romantic love, a love which they perhaps do not have in real life.

But viewers knew that there would be a sequel to The Empire Strikes Back and the sequel, Return of the Jedi did have a happy ending. However, Dune Part 3 is the last of the trilogy. Note that the final Spider-Man trilogy, Spider-Man: No Way Home was sad. Why this love of dark endings?

[–] ZC3rr0r@piefed.ca 1 points 3 hours ago

Given that the majority of movies has a happy ending (which can often fell forced as a result of sticking to a formula) I personally feel that breaking with that tradition (outside of genres that often go for downer endings line horror) is refreshing and can make a movie a lot more memorable.

To each their own, of course, but I'll be happy if the movie sticks closer to the books. There's a powerful lesson and symbolism in there that I hope stays preserved on the big screen.