One good topic would be the loss of spiritual meaning in the lives of the townspeople. When they find out that there is a man who might be a literal angel -- a supernatural being that is a direct representative of God -- in their town, they do not respond spiritually, but with coarse amusement:
...the whole neighborhood in front of the chicken coop having fun with the angel, without the slightest reverence, tossing him things to eat through the openings in the wire as if weren't a supernatural creature but a circus animal.
(Márquez, "A Very Old Man with Enormous Wings," salvoblue.homestead.com)
This disinterest in experiencing the supernatural extends to those who travel to see the angel; most are there simply to stare, while some desire miracles and healing. The keepers of the angel, for their part, use it to make money instead of searching for personal spiritual meaning, and are relieved when the angel leaves. A good thesis statement on this topic might be: "As humankind continues into the Modern Age, his connection with spirituality diminishes."