Good and reactionary, because the reactionary elements are mostly a deliberate subversion and commentary on the complex relationship between individual agency and large political movements.

Like Paul isn't a bad person, per se, but he can't find any acceptable way out of the trap he's been forced in to by the machinations of other people going back thousands of years. He knows the Jihad is coming but his attempts to avert it prove fruitless because one person, even a super-human who is nigh divine, can't exert dictatorial control on whole nations and belief systems.

The Fremen aren't evil, per se, but their beliefs and religion have been shaped by the deliberate manipulations of extremely canny political actors over the course of millenia. The incredible harshness of their world has imposed some very social darwinish constraints on them, and it has given them a very fatalistic and utilitarian view of the world. They've been subjected to countless generations of brutal imperialism by the wider galaxy. But they're not hapless victims; They have agency. In spite of everything they've been working with Kynes to secretly horde vast amounts of water with the ultimate goal of making Arrakis a green world. They've successfully concealed their true numbers and technical capabilities from the wider galaxy for a vast span of time. Despite Paul's super-human powers the Fremen have far more control over him than he could ever hope to have over them, as it is ultimately their beliefs that shape Paul's fate instead of the other way around.

The Atreides and the Harkonnens are both a condemnation of Imperialist powers; The Harkonnens are naked and honest about their imperialist violence. The Atreides, while genuinely well meaning, are still Imperialists and their Imperialism, while superficially softer, is just as iron-clad and oppressive. The Harkonnens order soldiers to their deaths on threat of retribution and torture should they fail, while the Atreides send soldiers to their death inspired by iron-clad loyalty to the Duke. But in the end, soldiers die and nobles profit.

The ruthless regime of Eugenics that the galaxy operates under is shown to give humans super-human abilities - Mentats are human super-computers. Darwinian brutality has turned the Fremen in to fighters without peer. the Bene Gesserit can move faster than should be possible and engage in molecular chemistry through fine control of their own endocrine and digestive systems. The Quizzical Hatrack develops powers of data processing, pattern recognition, and raw calculation so powerful that he develops a complete awareness of the past and future. Incredible things. But they don't bring anyone joy or peace. They just turn people in to more and more powerful weapons. There's no master race, no hint of humanity achieving a great destiny through genetic hygiene. The eugenics have just created new ways for people to harm and manipulate each other.

In a lot of ways the story is very grounded in materialism. The whole structure of the galaxy is explained in more or less sensible terms; The Fraufeluch system that limits what technology peasants are allowed to use allows the nobles of the Lansraad to maintain absolute control - Without access to high technology, even if a peasant rebellion succeeded, the nobility still controls space. They can interdict the peasants and starve them out or bombard them from orbit. But since technology is so strictly controlled, to the point where draft animals are used to pull anti-gravity wagons, and the caste system is so rigidly enforced, there's little risk of the nobles every losing control. The relationship between the Lansraad, CHOAM, the spacing guild, and the Emperor shows a system where economics rules and the balance of power is dependent on numerous different interest groups holding knives to each other's throats, but knowing that if they strike they'll be struck down. The Emperor has enough power to crush any one noble house, but the noble houses as a whole could match the Emperor. The Spacing Guild, with it's absolute control over the power to travel between worlds, can protect it's interests by simply denying anyone who acts against it the privilege of interstellar travel. They're all part of CHOAM, dedicated to maintaining the flow of spice that all of them rely on - For space travel, for longevity, for the enhanced mental abilities the nobility need to survive each others brutality. There's no fanciful absolute monarchs or arbitrarily strong villains. All the actors on the stage are there for a reason that is justified by the economic norms of the galaxy.

It's not all sweetness and love. Herbert had a very reductive view of Islam in many ways, and while it's a subversion of the white savior narrative it's still a white savior story. And it has other various problems. But a lot of it's staying power comes from the very complex work Herbert created and the way he uses that world to reflect on the nature of power, individual agency, religion, the weight of history that lies heavy on us all, and other serious topics.