Sorry you didn’t like it.
Ok so my thoughts on the importance of Dune and its legacy;
It redefined the SF genre which had become bogged down by Asimov et al. Its main ‘hero’ sits within quite a compelling journey of discovery, subverting aspects of the traditional Joesph Campbell mould.
The book has had significant influence with sequel books, films (x2) Warhammer 40k & Star Wars all resulting from it in some way or other but most importantly it gave us Command and Conquer on the PC.
Its ecological theme was ahead of its time; the balance of nature and the impact of human actions on the environment become an interesting ‘supporting statement’ to (US mostly) environmental movements of the 70s. The book was born of Herbert writing a magazine article about desertification in the US I think.
The characters in Dune are complex and flawed, not that likeable agreed but I find them very engaging. A political subtext (or perhaps theme) throughout the story reflects global power, governance, colonialism and political manipulation by feudal overlords & organisations. But it can also be more simply seen as being about jihad, oil and the people who want to control commodities.
The spirituality elements see an exploration of destiny / messianic themes, conflicts and fantasism in religion (machine vs myth) and the possibilities of human potential.
It won Hugo and Nebula Awards making it a pretty big deal within the genre. The sequels less so (even his own had little extra to offer the genre he had created) and the books written after his death seem to be of diminishing returns… although I haven’t bothered.
I appreciate its clunkiness and it throws you in at the deep end from the word go but I find it quite rewarding. Probably sits in top 50 books of all time (but I haven’t checked)
I’d give it 9/10 and I’m not really a sci-fi fan.