A circus should be limited to trainable animals that want to do the tricks. I grew up with cats. Some kittens were more timid, wild, especially if they don't know you. So, no matter how hard I tried, some cats didn't like me.

Sadly, people end up beating animals. Generally, people are motivated by money, greed, fame. Also, sometimes, it runs in the family and is passed on from generation to generation. So, obviously, people sometimes make bad choices. So, people become obsessive over what they can do. Sometimes, people either don't know or don't care that what they're doing is hurting other animals and other people.

I like zoos, forests, jungles, woods, farms, etc.

You could have dogs in a circus. Maybe dolphins. Maybe some birds. But if you have to beat an animal too much or even at all, they probably should not be in a circus. I guess you could have elephants walk around, as long as you don't abuse them. That's the tough part. Humans can take out their anger on animals. People can have problems with other people. So, people can feel angry, sad, etc. So, they can sometimes vent and take out their emotions and anger on animals. People are not aware of that. People also can beat children, which is also not good.