If you've read the book you'll realise that most of the important scenes come with commentary by the leading characters, which adds depth and explains what's going on. The film doesn't try to do that, and so loses that depth, and doesn't find any other way to supply it. So, the Bene G's breeding programme gets a mention, but just that; we're told Lady J was told to bear daughters, but just that; if you've read the book these are hooks if you haven't they are meaningless. Some scenes are problematic: Dr Yueh managing to bring down the house shields just about works in the book, but not at all in the film: everything is on such a vast scale that it is impossible to believe one man could do that. Plus disabling all the sensors that would have warned about the f*ck*ng enormous spacehips just overhead. In their efforts to be impressive, we have enormous lovingly-rendered spaceships landing and people walking off them. WTF? Have these people no motorcades? The battle scenes, whilst also lovingly rendered, make no sense: in no universe should people on foot rush at each other with swords, having decended from spaceships. In the book, of course, we know that shields don't let in high-speed items and this helps; the film doesn't manage to convey this well. In the book, when Paul kills Jamis, eventually, it is helpfully explained that the reason he keeps slowing down is this facet of shield-trained-fighting. Having Paul dream of a figure with a bloody knife doesn't convey the across-known-worlds Jihad. And so on.
On a perhaps somewhat pedantic note, but with just a tiny bit of thought it could have been done better: Dune is very very hot in the sun, yes? I've been to places - Greece, Spain - that are like that. If you walk across a courtyard in such a place, you take advantage of every shade. They don't. When Paul wanders across to talk to the palm-tree-waterer, he doesn't stand in the shade of the trees, and neither does the waterer. Little things like that - and people not keeping their mouths shut, despite having nose plugs in - disappoint.
From that, you can tell that I spent quite a bit of the film comparing it to the book, and inevitably finding the book superior - by which I think I mean, the story and images the book conveyed to my mind. But some bits of the film do work, and carry you along, and you can forget the book for a while. The ornithopters are nicely done. Some of the spaceships are kewl. The worms are decent. Backdrops are good.
The lead, Paul, works. The Duke is OK. Lady J isn't: too weak, insufficiantly in control; her character sacrified for Hollywood tropes.
Note: I should add that (per my review) while the book is dead impressive if you're say 16, it doesn't fare so well to an adult.
A few words about the David Lynch 1984 version, which we watched at home recently. Which was also pretty good, though it did drag a bit. I found Sting, as Feyd-Rautha, good (was there even a FR in this one?); Piter was well done too; by contrast the 2021 version doesn't do its characters so well. DL's version tried to convey too much by having characters moon off into the distance, which is kinda what the book did, but it didn't work on film.
On scale
The books and the films differ as to the "scale" of the various households. Hence, as noted above, some things that make sense in the book don't make sense in the films. In the book, Leto's household in Arrakeen is effectively that of a colonial governor; there's a housekeeper, the Shadout; and from inside they can look out onto the road, along which people pass. In the film - certainly the most recent - the scale is vast; driven mostly I think by a desire for dead impressive CGI stuff, with spaceships and buildings dwarfing human scale. And mostly empty inside, apart from a few key characters. Indeed a flaw in the film is that the key characters are not surrounded by a cloud of servants, as they should be.