It's really the latter. I know people will argue this, and I say this as someone that did enjoy World War Z, but Max Brooks isn't a great writer and has issues trying to fully explore a realistic take on WWZ and the shitshow that followed.So humanity doesn't regress to 18th-century tech how? if 1/20th of the human population lives in one city than industrial society likely ceases to exist so A: Either the wiki is wrong or B: Max Brooks can't work out population numbers
Plenty of people have argued this, especially the Battle of Yonkers, but I did just attribute to the fact that Max Brooks was also trying to write an entertaining story...which he did accomplish. World War Z is a fun read. But if you ever asked me if its a great book, I'd fucking laugh.