I'll just comment on this. If he despised allegory & didn't mean to put any in (which you & Citanul are both claiming), then perhaps critics are correct when they say Christians shouldn't be reading it because there's wizards & magic & false gods & the like & he was the father of the mainstream secular fantasy we have today that devolved from Christian heritage
Even if that is true, I dont think we are to shun secular entertainment because it can make you more aware of the world we live in & can be harmless. Paul says it's what comes out of your body God's concerned with. How are you thinking. What are you thinking. What are you doing in response.
I don't see what line you're drawing from "Tolkien didn't like allegory" to "Christians shouldn't read Lord of the Rings".
I also don't understand how you're concluding that mainstream secular fantasy devolved from Christian heritage. 21st century fantasy is a mash-up of countless myths, legends, cultures, and fairy tales from all over the world, spanning many centuries. Are you drawing some other conclusion?
I spent plenty of years living in the Christian "bubble" where any type of entertainment that wasn't strictly religious, must therefore be evil. And I don't think many can argue that "Christian" forms of entertainment, where it tries to replicate the secular, usually results in anything but a bunch of cringe and just plain awful material. Things that aren't overtly religious in nature aren't evil by default. God is the God of everything. Test it to see if it's offensive to Him, and if it's not, enjoy it.
Portraying something, or telling a story about something non-religious, non-Christian, or even something evil, is not in itself, evil. Is the evil thing being glorified in the material? That's a problem. Is it being portrayed as bad, and something to overcome? That's how it should be handled. Mentioning fairy tale elements like fairies, dragons, wizards, etc, is not evil. "Well, in some instances, dragons represent Satan..." Okay, but is that what's happening in THIS instance? No? Chill, then. It's just a story.