You might be mixing events up. She wasn't talking to her mother before Jessica drank the poison. Jessica even tells Paul explicitly that she can hear her daughter speak to her in the first scene after consuming the poison and I don't recall any scenes of them talking before then. Definitely before Paul drinks the poison.
I think for me with Feyd-Rautha, he doesn't really need to be some big all timer of a villain. At the end of the day, Paul is the pseduo villain of the story and Feyd is just an obstacle in his way and an another figure in Paul's revenge story. I'm not so big on Feyd as an iconic villain or anything either, but it's an enjoyable performance to experience.
As for the final battle you ask two things. So first, it's not explained in the movies and barely covered in the books but there are supposed to be sietches that have hidden manufacturing factories for stillsuits and weaponry. I think for purposes of the movie you just kind of have to not think about it too much and assume they get their materials from raids. I think a couple expository lines wouldn't have hurt. As to the second part I think the fact that the combined Sardukar/Harkkonen forces being so comprehensively overwhelmed works for three main reasons: 1 like I mentioned, they weren't expecting an attack on that scale which started with a nuclear strike. Granted you could argue that if the Emperor knew that Paul was still alive, he should have anticipated such a strike was possible. 2. The Emperor/Harkkonens never took the Fremen threat seriously. While they were effective in halting spice production, most of the galaxy could never confirm that there were several million Fremen living in the South. So going to Arrakis with the Emperor's full fighting force, they likely assumed the kind of guerrilla warfare that Paul and his Fremen were involved in would be easily deflected by sheer numbers alone. 3. The attack came as somewhat of a surprise. It happened as the Emperor was receiving the Harkkonens to discuss how to handle Paul but they weren't in the process of preparing for a large scale attack. They were essentially holding court and then out of nowhere they get blitzed by a confluence of a sandstorm, nuclear strike, sandworm attack, and a huge rush of Fremen infantry. I think there's enough context in the movies to establish these three points. The point wasn't to make the Sardukar and Harkkonen forces seem weak, just not expecting the degree of the attack they faced because the Fremen have been routinely misunderestimated as they (presumably) never fought united like that and had just been involved in guerrilla style raids. Paul's attack relied a lot on the Emperor/Harkkonens' hubris and fortuitous opportunism. How Paul coordinates a galactic holy war from that point in fairly short order, I don't know. I only read the first book and maybe there's some details I missed. As for how they got multiple people on the backs of sandworms, I couldn't tell you but it's one of those things where if I intentionally tried to question the logic of every fantastical thing I see in sci-fi for realism, I'd be unable to have fun with any of it.
As for the faithfulness to the adaptation, I mean that kind of gets you into a "can't win" scenario. If they change too much from the books, you have a bunch of die hard fans of the source material upset about creative license. If they stick to the source material too much you have people dissatisfied because they didn't quite get the story they were hoping for. I mean in the first instance, a bunch of Dune fans are upset because Denis dared to--heaven forbid--give Chani more agency and more of a moral compass than she had in the books. Personally I think Denis struck up a good enough balance.
As for more world building and characterization of the plight, I don't think shaving off a few long takes is going to leave you with enough time to flesh the story out the way you seem to be hoping for. I agree that things could have been explored more in depth, but on my end, I got from the movies what I need to consume this story for what it is. An example, the plight of the Rebellion in Star Wars is fairly surface level. You have an evil fascist government shown to be controlling the populations of a huge number of planets occupying a galaxy, but in reality, outside of blowing up a planet, Lucas' original trilogy never really shows any tyranny or how it affects the people of the galaxy. You just have rebels talk about how the Empire needs to be overthrown, a montage of planets celebrating the fall of the Empire, and a lightly developed allusion to the Empire governing Bespin's affairs. But you don't see the suffering of the people, you don't see freedoms being restricted, etc.. As hit or miss as the Disney era has been they did a lot more legwork to demonstrate the subjugation and control of Palpatine's empire than anything Lucas did. And that came after what, 11-12 hours of storytelling from Lucas' era of Star Wars not counting the cartoons? Here, the two films are pretty dense even with a combined runtime of 5 hours +. I agree that there's some corner cutting on the world building but I don't think you could add much more than Denis did without a significantly longer runtime or a three part movie and there's just not enough story for three separate films. For me I enjoyed what I got at face value as the world building was enough for me to get a sense of the stakes. Which is how a lot of people end up enjoying the original star wars films.
As for Paul's ease in ascendancy, again, I don't think it's meant to be a big struggle. The core and heartbeat of the story isn't from rooting for a good guy to overcome incredible hardships and obstacles. Like, to make the Succession analogy again, that's a story of shitty people trying desperately to claw for more power than they need and it's replete with obstacle after obstacle until the end. That works for that story because the spirit of that story is how cutthroat and despicable the corporate world can be and how people will fight for unworthy rewards. Dune is telling a different story. It's not about Paul overcoming big challenges to earn his power. It's far more about how Paul knows the consequences of the path he takes and the tragedy of watching him ignore that knowledge to take that path and become exactly who he was trying not to be, callous exploitation of natives and all. Maybe that's not as compelling a story for you as the traditional tales of heroes and anti-heroes overcoming adversity, but to me I find it a refreshing take on an epic/grand scale story and I would imagine it's why Dune (the novel) has such an enduring legacy to begin with. If you're looking for struggle, it first comes with Paul and Jessica defying all odds and surviving the desert and escaping the Harkkonens in part 1 and in part 2 it's the struggle taken by Paul and Chani for Paul to retain his moral center and identity by not giving into the path of a false messiah. From that perspective, the protagonists lose and lose badly. As for the characterization of the characters around Paul, I think we just have to agree to disagree. The characters got as much characterization that, to me as a viewer, they needed.
There's no heroes here except maybe Chani, Duncan, and Duke Leto. Gurney is devoid of morals once he finds a lust and hunger for revenge. Jessica has no qualms about leveraging the propaganda the Bene Jesserit laid for her son to be a false messiah and is even worse about exploiting these advantages with no moral sensibility than Paul who at least resisted, and she behaves that way because she is hungry to stay in power and get revenge for Leto's death. Stilgar's religious fundamentalism and devotion is so deep that he is ready to be a textbook sycophant for Paul even before Paul turns to the extent that he'd die for and wage genocidal war for his believed messiah. Aside from being comic relief he's written as an allegorical character for the dangers of religious extremism. The Baron is written as a conniving man willing to engage in any kind of depravity and duplicity to advance himself and his family to the point that he would have carried out an overthrowing of the Emperor if not for Paul's climactic attack. Rabban is written as the Barron's bulldog who is desperate to prove he is competent and worthy and increasingly loses his composure the more he fails. Feyd, I already discussed above. The Bene Gesserit are developed well enough as pseudo-mystic string pullers. Irulan is depicted well enough as being dedicated to holding onto power even as she sees the walls closing in around her father. Like I'll grant you that they don't really develop the Emperor much and they could've given him a few more scenes to give us more of what he was about, but past him I'm not really starving to know more about these characters I just discussed than I did after two viewings (trying to assume I never read the book). Even if I lacked the extra context I had from the novel, I didn't feel I needed more from these characters than the roles they served and the purpose they filled.
But like we've both said, it's all subjective. I'm just sharing my perspective when all's said and done. If these things didn't work for you, that's fine.
