Should we make up our own Gods?

In modern fantasy novels it’s very common for the author to make up their own deities. It is a tradition better honored in the breach than the observance. I don’t say it’s never appropriate, if you are writing about Ancient Atlantis or some place like that it’s logical to assume they would have some crazy pantheon of their own. But even in these cases there is too little use of the model Tolkien and C.S. Lewis used, i.e. giving new to the Christian Pantheon. I prefer to follow the model of the tales of Arthur and Charlemagne where we uphold Jesus as the true defender against the darkness. It’s something we need to be reminded of in this world which so often tries to deny that there is anything dark about the dark. In a world where it’s common to talk about killing fetal babies to make potions to prolong our lives, can we continue to deny the existence of black magic?