brown and white monkey on white metal cage

I absolutely love animals and will always try to help, either by feeding feral cats in my neighbourhood, adopting or donating to animal sanctuaries, but I still cannot make up my mind about zoos. On one hand, I understand the need of protection of certain species and that it needs to be done in a controlled environment. Same goes for rescued wild animals that cannot make it in the wild. On the other hand, there are a lot of cramped zoos where animals are mistreated and suffering only for the money of visitors. Is going to zoos helping animals or not?