HaroldTheHobbit
Hero
It may well be that Dune lives up to objective and traditional literature analysis standards of being a good book.No, it is actually great. I remember one of my undergraduate English Profs selected it out for a Junior Seminar deep dive (though he was mostly an early Novel guy), and it stands up to careful scrutiny. The characters and plot are less stock and tropey than you might assume at first. The prose is top of the line, and every element comes together in a perfect whole. It is simply a work of artistic beauty.
Genre literature however doesn't necessarily need to live up to those criteria to be seen as a good book within the framework of the genre. Sci fi in general is about raising the question of "what if" - if one change a specific parameter, how does that impact society and humanity. Sci fi is also first and foremost idea literature. Even with mediocre prose and flat characters it can be good within the genre framework if it treats an idea in an interesting way - Asimov's Foundation is a prime example.
So, if a sci fi book needs to live up traditional literature quality criteria, we have a very small pick of books to choose from. I mean that it's necessary to be aware of and have a deeper knowledge of the genre framework, and judge a book from within the genre frames and internal quality definitions, otherwise one can disregard the vast majority of sci fi as crap.
As for Dune, I really like it from an idea perspective. However, like for example Moorcocks work, it is plagued by a very dull prose typical of the 60ies and 70ies, with a kind of affected modernistic ambition that I personally think makes for a chewy reading, and pulls down otherwise interesting books.