Good to hear from you, Hal 9000. Hint: Don't trust Dave.
As for where everybody has gone, I wish I knew.
I love Harry Potter. It feels like fantasy to me. In contrast, the most recent fantasy I read, River of Stars by Guy Gavriel Kay, had only the least smidgen of fantasy in it. I gather it resembles a more romantic Game of Thrones in that respect.
As for the popularity of zombies, there are a large number of people, particularly here in the US South, who own semiautomatic weapons and would dearly love to kill large numbers of people with them. But they know, in their hearts, that killing people is wrong. So they fantasize about killing zombies.