It warned about AI. It showed a fictional interplanetary civilization 10000 years after an anti AI jihad.
That is true, but the original series by Herbert didn’t explain much about the previous 10k years except to name it and that’s about it. It wasn’t until the prequels written by his son and Kevin J. Anderson that the reader actually found out what started the war on Thinking Machines. The sequels by that same pair then explained how they (actually just Erasmus) had guided humanity for millennia to the point that the Machines and humans could co-exist.............