u/GumboSchrimp

The idea is to get energy with dragonair or attack with D,nite and then switch out into a Juggled Flygon.

It's clear that Aang did not master earthbending or firebending, by his own statement about fire, as well as Toph saying his earthbending wasn't up to par.

However, there was no mention of his waterbending prowess by Katara.

I assumed Aang mastered waterbending due to beinga faster learner than Katara, who was a waterbending master in book 1 or book 2.

I also get that airbending is the only bending art with a criteria for mastery, so it's hard to say for the other elements without your master's approval.