I love going to the zoo, but I understand your concerns.
I get it. When I was a kid, the zoo was a magical place. I loved it. I dreamed of working at a place like that. I always thought "when I grow up and have money, I'll visit every weekend". Instead, as I grew up, I started visiting less. I just can't do it anymore. I'm not saying I'd never go again, but it's not likely. I don't enjoy it anymore.
I always knew that life in a zoo was not nearly as good as life in the wild, but as I got older, I realized more and more just how true that is. I think the last straw for me was seeing Stella the jaguar laying in the exact same spot every time I saw her. Just laying there, gazing into nothing. I took three or four photos exactly like this over the span of 5 or 6 years. Nearly every time I've seen her she was in that exact same spot, with that same look. Other animals, as well.
I tried to ignore what was obvious. I thought about how safe and well fed she is in her enclosure compared to the difficult wilderness. She's also likely to live twice as long in captivity, but at what cost? A long empty life isn't a life at all. All I could do is look at her and think "clearly this is an animal not enjoying life." People are standing around smiling and pointing at her, and she's suffering. She's forced to be on display in a very small exhibit, with nothing to do, not even so much as leaves to brush against. She lives with her thoughts and nothing else. She's likely the most beautiful (non-human) animal that I've ever seen, and I really wish she could've enjoyed life.
A few years back they paired her with a wild-caught jaguar named Pat and she had two cubs. She watched one of them get killed by another male jaguar (possibly another cub of hers from a couple years earlier) mistakenly let into the exhibit by a zoo worker. There's no doubt that deaths like that happen in the wild all the time, but there's a difference between it happening naturally rather than it happening in a small enclosure with no chance to hide or escape.
I do think that some animal species can handle captivity a little better than others. It's usually obvious which animals are relatively happy and which aren't. Those that have larger enclosures with more enrichment tend to be happier, but that's not always true.
I also know that Pat the jaguar had only two options: Death or prison. He was killing livestock in Belize and they chose to put him into captivity instead of killing him. Between those two choices, it's better that he was put into captivity. He died last August.