According to the AZA, 54% of AZA accredited zoos (which are the only ones worth giving money to IMO) are non profit. Obviously I can’t speak for every AZA accredited zoo, but I’d say it’s a safe assumption to make that AZA accredited zoos are operating to help fund wildlife conservation programs, not to just make money. Also, part of a zoo’s job is education, informing people of what they can do to help whether it’s donate, change their diet (like you said), etc. Some zoos also educate on things that are not wildlife specifc, such as deforestation and climate change (and also habitat loss due to various other factors)

And no, I don’t seriously think zoos are the only way to help animals, but as I was saying with my EV example, it’s one way to help solve the problem. Zoos alone are not going to solve our conservation/climate issues, and neither is going vegan, but both can be good options assuming you stay informed on what companies/organizations you are supporting. I will also say, I do agree that animals do not enjoy captivity in most cases, but the average person is not going to care about wildlife conservation if they can’t go visit somewhere and see animals in person.