I was prepared to be disappointed by the explanation for the Burn, but I kinda... wasn't. In a season whose theme is trauma and its aftermath, shown at both the personal and civilizational level, the Burn being the product of a single child's pain worked for me.
The production design for the episode helped a lot. I loved the Escher stepwell and the tower, though in part because it looked like a video game while having solid intradiagetic reasons for doing so, ie it was a video game, sort of.
I don't think Trek has ever come closer to being a science fantasy fairy tale. I feel like this is something Harlan Ellison could have written (and Rebecca Sugar could have re-written after Ellison was fired). I agree it felt of a piece with some of TOS's more gonzo conceits. Like the stone time donut that allowed a high AF McCoy to temporarily eradicate their entire timeline...
I like the bizarre fever dream danger of original Trek (which is present in the TNG-era, too, to be fair). It's nice when makes the occasional reappearance. And I'm also looking forward to see what kind of ethical dilemma is in store next week -- they really should have named the planet Omelas IV or something...