I went through a period of not approving of zoos about 25 years ago. Then started reading articles about how young children in cities don't have any exposure to rural animals, let alone animals from other continents. Plus, there are species who last longer for being in captivity (RIP White Rhinos).
As long as there are morons out there who think killing animals for fun is a good idea, then zoos are a better idea.
Not to mention poachers, but that takes us back to the "they need alternate income streams" discussion.