I don't remember Legend of Korra changing anything. I thought in Avatar: The Last Airbender it was always established that some people were born with the ability of bending and most others weren't.
I also never felt like the original Star Wars movies made it seem like anyone could be a jedi. Luke and Leia were "strong with the force" because their father was a jedi.
If there was a world where literally anyone could have superpowers then who wouldn't have superpowers?