As someone who didn't read the book, the dune adaptation felt pretty hollow. A lot of visual splendor, but a very thin story with very empty characters. Extremely shallow interactions.
The protagonist is basically an aspergers teen under a great deal of pressure, including multiple murder attempts against himself and his family and friends. He also happens to have visions of the future. Before he gets marooned into a planet made out of psychedelic dust.
Considering that, I think the interactions were too articulate. Trainspotting was Dune with less drugs and internal conflict.
The books have notoriously rich plots, which is why they were deemed unfilmable.
There was a lot left unsaid in the film to keep it concise and uncomplicated for a viewer like you who hasn't read the books. (Perhaps it was an overcorrection.) The director would occasionally reduce a long meandering sideplot to a quick distrustful glance from one of the characters. Someone who's read the book would pick up on it and feel like it did the book justice by acknowledging those events rather than cutting them out entirely, and the film doesn't burden viewers who haven't read the book with an impossibly hard to follow plot crammed into 2 hours.
I don't disagree. As I mention in my earlier comment, the point is that what was once considered unfilmable has now actually gotten adaptations, even if the adaptations might not be good.
And what might be attempted once might receive adaptations again, until someone gets it right.
I always interpreted it as "unable to be adapted faithfully."
For instance, in my earlier post I mentioned the live-action Ghost in the Shell, which in some parts Hollywood almost-mechanically adapted to be shot by shot identical to the original animated film, while completely missing the point with the racebent casting choices and much of the writing. I would count that as a poor adaptation, but not adapted so faithlessly that it has no resemblance to the original work.
Then again, Blade Runner is a loose adaptation of PKD's original story, yet does its central themes justice. So I guess "unflimable" is a relative term. Maybe it could ALSO just mean "no demand or desire to see adapted for film or television."
My overall point is that it's a golden age of IP and with the mainstreaming of nerd culture (and the endless demand for content from the streaming studios), all sorts of works that were once considered unfilmable are about to see the light of day.
"Unfilmable" for me is James Tiptree Jr.'s "Up the Walls of the World". Half the novella is spent on a gas giant inhabited by giant telepathic manta rays farting jet fire. The other half is spent in the <body> of a solar-system spanning semi-material, invisible/ dark <creature-ship-machine> where all the protagonists are transferred as disembodied minds. The day is saved by a strong telekinetic/ telepathic computer programmer who merges with the <beast-thing-machine-of-the-stars> and a spontaneously arisen AI from Earth (early '70s too... It Came From The Mainframe).
The movie doesn't even cover the full plot of the first book. I'd say the first 3 books are easier to adapt to screen, God Emperor later becomes impossible to adapt cause most of the book is internal monologues.
I think it's supposed to be part 1 of a longer series of movies. While I haven't read the book(s?) in ages, I can remember that there's a LOT more that needs to happen.
Considering that, I think the interactions were too articulate. Trainspotting was Dune with less drugs and internal conflict.