I think the alternative is that our brain, somehow, is connected to some metaphysical aspect of reality which is what most religions believe.
"an", not "the" alternative.
Consciousness can be not-emergent but also not metaphysical, think sci-fi-type undiscovered physics or matter.
Another alternative is that consciousness exists on the map, and unfortunately we're confusing that with the territory.
The counter to that is that altering the brain directly alters the consciousness. I can take LSD and I literally change. I can have parts of my brain removed and parts of my self disappear. It's not like cutting off a leg, where I lose capabilities but am still the same me.
The logical conclusion is that the brain makes me.