Some people have stated that as of the 11th season, South Park has started a trend of leaving behind their politically biting satire for shallow spoofs; but this could not be further from the truth.
While this episode does spoof the Living Dead series, there is more. It is a satire of how people treat the homeless. Characters say things like "They're pretending to be just like us" or "They want to be human." This episode attacks a culture of people who ignore the lower class who are often just down on their luck.
So yes, it is still a satire, and also a wonderful spoof. What more could you want?