>there are cross shaped parasites that grant eternal life

Without giving away any spoilers to the books, the parasites are only that on the surface. If anything, the books present a wary picture of religion, especially the last two Endymion books, but also a wary picture of technology.

> the first book is literally a retelling of the The Canterbury Tales, all the characters are on a pilgrimage.

As we have both read the books, it's notable that you associate pilgrimage with Christianity. This illustrates the point.