Different tastes. Tolkien hated Dune, and I think LoTR is all style no substance.
Every now and then I go for a reread, hit a passage talking about a magic sword and the book trying to rawdog convince me that this sword (dagger?) is super cool and awesome by... well outright saying '"this sword is super cool and awesome" (trust me, I'm the narrator) '
I've read all dunes books 8n French, and the version I've read were old and weirdly written, I thought this was a bad translator. Fast forward 15 years, I mostly read books in English, and decide to give it a go again. I think it's worse. Probably my standards are way higher now for fantasy and anticipation (I do not thank you Sanderson).
Still, I now understand Dune better and now think it's a fantastic story if you manage to endure the first ten chapters.
I like Sanderson because he's consistently good at world building and the story itself. Sanderson is one of the best and most consistent world builders in fantasy writing. His magic systems are all interwoven into his societies and reflect the impact magic would have on every day life. His characters are still quite weak, especially women. His prose doesn't seem to be anything special but it's also not a distraction. His mix of world building and story telling more than make up for those weaknesses in most cases.