The angel and the spider-woman -- a giant tarantula with the head of a woman -- are both examples of seemingly supernatural creatures that are treated with contempt. Instead of being astonished by these creatures, people use them for personal profit and treat them like animals. They are both confined and under constant observation, without personal privacy; they are closer to scientific experiments, except that no one takes such an intellectual view:
At first they tried to make him eat some mothballs... in the end [he] ate nothing but eggplant mush.
Her only nourishment came from the meatballs that charitable souls chose to toss into her mouth.
(Márquez, "A Very Old Man with Enormous Wings," salvoblue.homestead.com)
The meaning that can be taken from these two unfortunate creatures is that humankind no longer cares to take a spiritual view of the world. The angel in particular is taken in stride by almost everyone who sees it, and they react not with surprise and awe, but with amusement and disgust. The overall meaning seems to be the loss of spirituality, and the change from religious meaning to mundane meaning. Instead of inspiring religious fervor, the angel inspires its keepers to make money from pilgrims, and so any moral lesson it could have taught was lost.