But human minds are too complex for us to do this - so we attribute its operations, which we cannot comprehend, to chance. Ignorance is the key.

I'd agree that ignorance is the key, but not that people in general attribute the operations of the human mind to chance. Rather, it seems we attribute these operations to a noumenal essence that is somehow neither deterministic nor random. We make this attribution so readily (and not just to other human minds) because that is our internal experience -- the feeling of our algorithm from the inside.