Mechanistic rhymes with:
anachronistic, antagonistic, chauvinistic, deterministic, expressionistic, hedonistic, hellenistic, humanistic, impressionistic, anachronistic, antagonistic, chauvinistic, deterministic, expressionistic, hedonistic, hellenistic, humanistic, impressionistic, opportunistic, stalinistic
Mechanistic sounds like:
machinists, machinists', mcnuggets, misogynists