Aang is kind of mid as a bender,

Aang was a prodigy as an Airbender, he became a master at the age of twelve and invented new techniques. He was mid at the other 3 because he hadn't had time to practice.

But I do agree with your overall point. Animes are usually good on this trope because they love the idea of training super hard. That has it's own tropes of bootstrapping, but I love how in the DBZ verse you can just do martial arts hard enough and learn to fly.