Ironically, one of the reasons Roman Paganism basically died when Julian the Apostate tried to revive is that he was essentially *turning it into Christianity*, and turning something into an inferior copy of something that already exists is the fastest way to destroy it. (Which is coincidentally why Modernism has massively shrunk the Church, because its an attempt to turn Catholicism into Protestantism mixed with Judaism, of course it will end up killing itself and Catholicism will rise again stronger). I would imagine a lot of the Roman practices jewish anti-theists deceptively cite as being stolen by Catholicism were actually the products of Julian's machinations, though sadly my knowledge of the subject is incredibly limited.