This italicized passage has been copied from an article on CS Lewis and James Blish. See here. One section of the article, called "Ten American Future Historians and Four Related Authors," summarizes coverage of religion in several future histories, including Anderson's.
Why does Aycharaych pity God? If God is omniscient, then He lacks mystery. But, if meaning is in mystery, then God has no meaning. And, if God is immortal and death is completion, then God is incomplete. I think that Aycharaych's conclusions follow from his premises although I do not accept the premises.