I think one problem is that DUNE should not be an overshot improvised experimental film since it's based on a hugely successful novel. That's why Lynch was always the wrong choice, same with Jodorowsky though I would have loved to see his version. I think it's unfilmable.
I don't disagree with this. But it's the fact that Lynch was such a perversely ill-fitting choice that makes the film fascinating for me. Universal wanted the next Star Wars, but De Laurentiis hired the guy who did Eraserhead to make it. How does something like that happen? Lynch had only made two movies at that point, one a micro-budget art film and the other a stately black-and-white historical drama. Neither even remotely suggested that Lynch would be the right guy to make a big-budget sci-fi epic. Yet there he was, trying to bring his idiosyncratic vision to a project way out of his depth.
Dune is still one of the strangest big-budget tentpole movies ever made, and that's why it has endured with a cult following. Had a more conventional director been assigned to it, the movie would have turned out very differently. Perhaps it might have made a modest profit, but it also probably would have been mostly forgotten by now, like so many other attempts to ride the coattails of Star Wars at the time.