Boring. Think about it, all they do is sleep, eat and be pampered. There is nothing to look forward to.
Animals in the wild have a way more exciting life. Yes, they have to fight for survival and food, but their lives are full.
Most domestic animals lose their survival instincts and really spend their lives vegging. They only have to look forward to walks and attention.
I don’t think to be an animal especially a cat and/or a dog, let alone a caged bird or confined fish would be very exciting. I love to see animals allowed to be outside to explore and not be confined to the lounge and indoors.
No, it would not be nice to have a cat or dog’s life. We are a cruel species for subjecting them to confinement.