I was raised with the understanding that religion is, at its core, a thing that exists in order to facilitate relation between a person and something other than that person. This relation manifests in a myriad set of expressions and forms, from the most obvious and essential of relating to the divine powers, to the (perhaps equally important!) social side of relating to your corporeal community, and a thousand shades of grey between these two polarities. Religion that does not promote, facilitate and structure a person's relation to something which is both bigger than and at least in some way separate from themselves is, by my definitions, not religion at all.
My father, a Protestant Christian preacher, taught me – drawing upon the philosophies of his grandfather, also a preacher – of a "trinity" of religious relational foundations which was altogether a different thing than the usual "trinity" spoken of in Christianity. He taught me about the equal importance of relation with the divine (or invisible) world, relation with the human (social, communal) world, and relation with the natural (physical, visible, non-human) world. This, which in so many ways served as the first three swings of the machete through the heavy brush obscuring the paths of my own polytheistic religious calling, was my first encounter with truly ancestral wisdom.
The inherent requisites of this three-fold paradigm are clear: for relation to the gods, relation to humanity, and relation to the natural world, one must accept that all three of these are real. "Belief" (orthodoxy) is of less importance than practical acknowledgment (orthopraxy,) whether through full submission or reluctant choice to not contest or challenge these things. Belief can certainly be helpful (or even preferable) in many cases, but one does not need to believe in al-Girtas to be in relation with them! A second essential and perhaps more subtle requisite postulation is the suggestion that these three-tiered worlds can indeed relate back to you.