Short answer: Noh is highly ritualized but not typically classified as "ritual theater" in the strict anthropological sense.
Ritual theater (e.g., Oberammergau Passion Play, Balinese temple dances, Navajo Night Chant) is performed as a religious rite—its efficacy depends on correct execution within a sacred context. The audience participates as congregants.
Noh, by contrast, became a professional theatrical art patronized by samurai elites and later the public. While it retains ritual form and aesthetic, its primary function shifted to artistic expression and entertainment—even if deeply spiritual in tone.
Noh is a classical theater with ritual roots and ritualized performance conventions. It occupies a unique space: neither purely ritual nor purely secular theater, but a refined art form that preserves ritual intensity within a theatrical frame.