An essentialist theory has to see essences as primarily intended, and so cannot see individuals as such as primarily intended. Thus God did not primarily intend to make persons, but human nature, which just happens (by some theories, anyway) to require persons to exist. But the notion of person is too integral to Christianity to be treated as an afterthought.
Said another way, on Aristotle’s account of things it is the essence or unchanging species that strives to participate in the divine as much as possible – the individual is more or less accidental. Christianity makes personhood divine in its account of the Trinity(and so makes creation a participation in persons) and makes the primary locus of divine participation the individual choices and life of the person.