For those unfamiliar the Dune series, the Butlerian Jihad was a crusade against “thinking machines”. Ultimately computers, and intelligent or thinking machines, even down to calculators are destroyed and banned. Humans who are trained in complex mental maths become known as Mentats, a sort of human computer. Just, uhh, leave all that shit on Bene Tleilax, with their Axalotl Tanks out of it.
Edit: had wrong planet name. IX -> Bene Tleilax
and then you have Warhammer 40K where Big E said that AI is heresy cause it practically wiped out mankind. buuuuut “machine spirits” and all that? yeah that’s fine as long as a competent human or semi-human is at the wheel. except very few of them actually know how anything works. I mean hell they have these walker things that they can’t turn off cause no one knows how to turn them back on.
real talk; the answer is that the Mechanicus are too powerful for the Imperium to actually fuck with. For one, they were an already established and very strong empire on Mars while the Emperor was just getting humanity back together after a great collapse on Earth, so they negotiated the alliance from a position of power. For two, the Imperium gets every gun, every ship, every tank, every drop pod, every Titan, literally everything other than I think food and manpower for their armies from the Mechanicus. If you wanna start investingating their “definitely not-AI,” you gotta be prepared to have your shipments of Leman Russes to suddenly start getting lost.
It’s not so much that the machine spirits inside of everything are FINE they are just impossible to exorcise, so they try to work around them and please them. The Omnisiah is different.