Ha, I'm admittedly kind of a sucker for faith narratives, so that was actually one of my favourite parts of the book! The murder was super interesting too, though.

which basically amounts to a church falling out of the sky and crushing his characters, leaving just their feet sticking out like the wicked witch of the east.

I hate you, I had this yummy mouthful of vanilla almond milk and you just made me snort it out.

On the basis of instinct alone I'm inclined to agree with you about Robinson's narrative feeling organic and Greene's forced. As you said, Greene just kind of uses Catholicism as this deus ex machina (almost literally?) to make his characters do things/go places they otherwise wouldn't. But then again, I've never been a lapsed Catholic.