Cultus in a sentence as a noun

So I think that's because he neglects the human aspect and if it's a cult if is insufficiently a cultus.

Probably not, the Latin "cultus" means worship of a god and is value-neutral; the vernacular English meaning of "cult" as "new religious movement that I don't like" is quite recent.

Cultus definitions

noun

a system of religious beliefs and rituals; "devoted to the cultus of the Blessed Virgin"

See also: cult