I think that it is what you know of the history of animal domestication and of pets that makes you think that there is an acceptable and low amount of suffering.
I think most people are aware of animal cruelty in factory farms (the chicken in cages, the pigs in cages, etc.), which represents 90% of all farm animals globally (https://www.sentienceinstitute.org/global-animal-farming-est...).
For pets, I don't think you understood what GP was saying: pet breeding involves massive amounts of death of puppies/kittens that aren't pretty enough or don't manage to survive infancy, the female breeders are basically confined to cages and "producing" all their life, some short-nosed breeds of dogs and cats are even illegal in some countries because they spend their life unable to breathe properly, pets are abandoned and killed, etc. The happy pets you see in the street are not representative of what it is to be a pet. But yes, these ones are not suffering.
As for long and harmonious, as much as we tend to see anything in the distant past as innocent, I'd remind you that the systematic killing of male chicks, the killing of veals to avoid them drinking all the milk, the killing of all animals as soon as productivity drops beyond a threshold, are not new practices. No animal wants to be enslaved. Same as no human wants to be enslaved.
I'm not attacking you, just attempting to give you an idea of why other commenters believe animal domestication is not ethical.