So, as an SF reader, you found Austen's Persuasion to be superficial, and complained that you had already worked out the entire story in the first twenty-odd pages, becuase you're used to stories with more depth; but when a "mainstream" reviewer reads a zombie story and wonders if the zombies constitute some kind of metaphor, he's being foolish and missing the point?

Hmm, interesting perspective.

BTW: "Yes, they make excellent symbols, and metaphors, and have kick-ass mytho-poetic resonance to boot. But their main job is... to make us begin to see the world as a place colored by our own zombie contingency plans."

Redundant use of the word "but", I think.