Supernatural beings from pre-Christian European religions, such as fairies, pixies, elves, gnomes, and so on, have been relegated to fairytales or folklore for children.
Easter eggs and the Easter bunny are relics from pre-Christian fertility symbols. The resurrection of the crops was supplanted by the resurrection of Christ.
And the roots of Santa Claus are probably ancient Norse/Germanic religions, perhaps a connection with Odin and Yule. He has been Christianised by being identified with St Nicholas of Myra (St Nicholas/Claus).
Whether there was an intention of original religious leaders or rulers to suppress the supplanted religions by making the beliefs "childish fantasy", so making it seem unmanly/unwomanly for adults to hold them, or whether it's something that happens sub-consciously within a community as a kind of viral folk memory, might be an interesting discussion.
Fundamentally there isn't a difference between modern religious beliefs and supplanted religious beliefs. It just depends on what religion was held or favoured by those in power; in the case of Christianity, that was the Roman empire and those who later replaced it, when it was part of the political power base; although the religion has diversified by the adoption into it of some pre-Christian elements.