If you want to build the "assume a spherical cow" zombie world, sure. But the zombie genre tends to be based on the dynamics and interactions of actual humans.

If you want to build the "assume a spherical cow" zombie world, sure. But the zombie genre tends to be based on the dynamics and interactions of actual humans. Romero's zombie movies are famed as social commentary, and you can (and people probably have) written entire graduate theses on what's going on in those films. World War Z (the book, I haven't seen the film) explicitly has wealthy people using their resources to hide their infected status and spreading the infection as a result, some governments opting for tough-guy responses that make things worse but at least calm people down a bit, others deciding to protect favored racial/ethnic/economic groups while leaving disfavored ones out as literal bait, etc. etc. That's mostly what the zombie genre is for, to comment on things like racism, economic inequality, etc. without risking the knee-jerk responses that would come from just explicitly saying "we live in a society that has these problems".