It seems more fantasy vs. "extrapolating from interesting science". The "Butlerian Jihad" was the core concept (and interesting), but all the stuff about folding space, neo-feudalism, etc. doesn't follow from that. You could get "rejection of technology, regression" in a cleaner book I think.

Actually, Vinge's True Names would be top on my list (and only 90 pages or so).

Sci-fi as a genre is not defined by "extrapolating from interesting science". It can also extrapolate from uninteresting science.