i.e. In ancient Europe and North Africa a Priest of Isis, or a Priestess of Jupiter would be a specialist. In modern Paganism, I’ve yet to see a coven/church/ etc that is formated in this way. Some specialize in an entire Pantheon, others in an Eclectic mix of pantheons. Still, Neo-pagan churches are more generalized than their Paleo-Pagan counterparts.