Very surprised by your comment.

-- Spoilers ahead. --

The Bene Gesserit spent thousands of years selectively breeding humans, and training them extensively in physical and mental practices designed to strengthen their endurance, control, acuity, subtlety of mind, physical prowess, internal consciousness, grasp of social psychology, political acumen, etc etc. People call them witches, because they just seem to know things they shouldn't know, but we as readers constantly get the inside intel, the reminder that, there's no magic at work here, they just pay attention, think critically, and know how to act to shape people's perceptions and motivations toward their own ends.

(I shouldn't say "no magic", I guess. The lines blur with the ritual substances, the visions. But they still typically strike the tone that these things emerge from control and mastery of mind and body, not the supernatural. The breeding program, the whole point of it was to "Shorten the Way", ie shorten the way to the supernatural.)

Paul comes from this deep heritage and training on his mother's side, with all the genetic favors that come with that, and all the environmental factors of a fully trained Bene Gesserit mother who spends a great deal of her time training, teaching, and raising her son. In the context of the two of them living in a noble great house as the Duke's beloved mistress and the Duke's beloved son and heir.

Now when we consider the father's side, the heritage and station of the House Atreides, and also the station of Paul, heir to the ducal fief. House Atreides, not merely a family with some money, but a real duchy, a "country" comprising entire planets, with a top-notch military organization, extensive business interests in every industry of society, and all the talent that attracts to well-run organizations that treat their people right / do the right thing / live with virtue and honor. Now whether that's Atreides PR or a fair description, they definitely hold this reputation, and hold earnest and deep-felt allegiance from several truly fine thinkers and warriors. Gurney Halleck, the bard-warrior, with an unlimited memory for quipping poetry and song and scripture, but a fierce talent for war. Thufir Hawat, the trained Mentat, human ultra-computer, loyal to the Atreides for generations. Duncan Idaho, Swordmaster of Ginaz.

Now we can see Paul surrounded by the finest men and the finest woman (Jessica) in the Known Universe, all of them training him from infancy to grow ever stronger, ever finer, ever subtler in his thinking, ever more designing and powerful. Bene Gesserit training and Mentat training, simultaneously. I don't mean that the book mentions them doing these things, I mean the book spends a great of time actually developing these things for Paul (and the reader), asking deep and philosophical and practical questions about the nature of power, the nature of life, the tragedy and danger of the galaxy, the weirding possibilities for those who can perceive correctly, can design a new system of action correctly and expeditiously. Lay plans within plans within plans.

So I understand if you think this all represents a bit too much, a bit overpowered of a character, not an unreasonable reaction I guess. But to say the book doesn't motivate any reason to believe Paul as a character, I just don't understand. Especially because to your point, he does not triumph!

I think you might not have understood the ending... Paul rides his abilities and powers to activate and lead the Fremen, by which I mean, activate the completely manipulative psychological scheme implanted by the Bene Gesserit generations ago. Paul proceeds to win the Fremen to him personally, win the planet back from the Harkonnens, and win the Imperial game of simultaneously thwarting the Emperor's intention, then holding the Spacing Guild at his mercy, then proceeding to marry the Emperor's daughter and secure his political primacy among the Landsraad, the Guild, and the Bene Gesserit. And then what happens? The Fremen proceed to go on a jihad across the entire galaxy, killing hundreds of billions.

The protagonist does not triumph. The book ends at the height of his triumph, but with the haunting knowledge of the fire of jihad that will now proceed to burn across the Universe.

--

I'm not sure "shallow" describes Dune accurately. I want to say something like, perhaps it contains shallow characters, or apparently shallow characters, who exist in a (spiritually) shallow Realpolitikal game in a dangerous class society. As people, they spent a great time of their time and energy analyzing the intentions and motivations of others, but also we see how, they pretty much need to exist in that state of paranoia and counter-scheming, or wake up dead.

But the book itself feels quite deep to me, as it unfolds and provokes new thought, new perspective. "The tangential slash of her question shocked his mind into a higher awareness: sand through a screen."