The sacrificial system, circumcision, festivals (Yom Kippur, Passover, Rosh Hashana, Pentecost, etc..), legislation (10 commandments, dietary), liturgy (priestly duties and garments), marriage and social laws, ....
That's not necessary for Religion.
My definition:
" A Philisophical approach or framework to one's life, including traditions and customs, that shapes the way one interacts with both the physical and/or metaphysical aspects of sacred reality. "
None of this requires a sacrificial system, or festivals, or written laws.
Those are just outward constructs. Illusion.
Although, for those who have forgotten, those things can be good waypoints to guide one back into their own sense of Wisdom with the world.