There is more than one type of dog. Many among the multitude are both capable of living in a small apartment, and not having genetic medical issues.

Some dogs are good in apartments. My hound is a total couch potato, you have to drag her off the couch to get her to go for a walk

There’s nothing wrong with adopting sick breeds like pugs. Just don’t continue their breeding.

Eh, it's a bit like buying ivory products (tusks, not soap). It encourages the breeding.

Buying a pug, I’d agree because it more directly comes from the breeder. As far as I know there’s no way a breeder or previous owner would know their dog is being adopted unless they’re actually making an effort to check in with the shelter. Regardless, they get no money out of it sending them to a shelter.

Also dogs that don’t get adopted are often killed making it an ethical choice.