AI and robots do exist in the Dune Universe, in the original Frank Herbert books but they were part of the long-lost past.
In the first scene of Dune: Prophecy, the viewers get a glimpse of Butlerian Jihad, which is the great war between humanity and Artificial intelligence. Eventually, humanity wins leading to the ban of the latter. This becomes one of the most important events why computers and thinking machines are strictly forbidden in the Dune Universe.
In more than 10,000 years between Dune: Prophecy to Dune movies there will be no significant technological advancement. But the reason is more complex than it seems. Read further to explore in detail.
Stagnation of Technology is Important in Dune: Prophecy Universe
Stagnation of technology is important because this is what Dune is all about. This situation is supposed to induce shock about how long it is going to last. With the end of Jihad and the large-scale spice production, sophisticated technology was no longer necessary. Therefore, society is inclined towards a more feudal structure which is not great for fostering innovation. This further benefitted the people in power and any technological innovation is quickly discarded by the ruling power.
Dune stands shockingly relevant to our society and reflects the core of our society where men in power are using machines to control the rest of humanity.
Dune: Prophecy explores the potential evolution of Humanity
In Dune: Prophecy Mother Superior mentioned the purpose of human advancement. By this, she doesn't mean humanistic or progressive advancements but instead exploring the means to be a human. Expanding the limits of the body and the mind altogether.
However, Bene Gesserit does want to prevent human extinction but is also aware of the fact that society's stagnation is inevitable and is bound to happen. Therefore Paul became the first change in the power structure when the hierarchy was flipped upside down and the marginalized were given power and authority. The next challenge for humans was to protect themselves from external threats and survive, while technology became taboo for the time being.
In Dune Universe, humankind is using machines as a crutch. The machines are defiling human development. So, after the machines are gone humans need to find other ways to hone their skills. Therefore, Herbert is focusing on the potential evolution of humanity rather than muddying things with the advent of machines.
For Dune, this stagnation has always been at the heart of Frank Herbert's writing, and the technology issue has been the center of the story. In addition, the feudal system engrained deep into the society that was devoid of any technology and actively discouraged technological progress, reasons why it took millennia for technology to reappear.