I don't think the site is claiming otherwise.
And as for Frank Herbert's Dune, I gave it a try. I read the first two books, and was 20% of my way through the third when I realized that "No, this whole story is not going to get good ever."
Should have just stopped after a few pages of the first book :-)
Ha, I love Dune personally, but it definitely doesn't get better after that.
It's a good thing that people have different preferences
My most recent read of Dune was after Foundation in order (side bit: bailed at Foundation's Edge because it got too "preachy").
One of the things that I had stumbled across was that Dune was an argument against the utopian view of Asimov and Foundation where individuals don't matter in the Seldon Plan and its played out in a galactic scale. Dune in that read is a dystopian view of the future where everything (at the galactic level) hinges upon individuals and the plot is played out on a planetary scale.
Asimov was asking "can reason organize civilization?" and Herbert came back and asked "what are the dangers if you think it can?"
...
So, when I revisit the large scale science fiction from the era... to me, now, it's more of a philosophy paper with a plot founded in future speculative fiction - more akin to reading Plato than Tolkien. Philosophical arguments rather than myth making and story telling that the authors were dueling in serialized pulp magazines rather than letters and treatises.