Let's say you are playing a deck that has a really unfavorable matchup against zoo, and you are playing a lot of zoos on ladder. In that case, why do you continue to play that deck? If I'm playing miracle rogue and encountering a lot of handlocks, I will lose a lot because my deck isn't great against handlock. Does this make handlock OP? No, it just has a good matchup against what I'm playing. If I was seeing mostly handlocks I might switch to rush hunter. If you are playing a deck that sucks against zoo, and you are seeing a lot of zoos, switch your deck!
Also, if it weren't for zoo, there would be more people complaining about the game being pay to win. Without it, there would be no low cost decks that can compete with high cost decks. So how can you guys complain about it?