For a show that's progressive, one-of-a-kind, ground-breaking for its time, and relies on "Show, don't Tell" a lot throughout the series, it bugs me how ATLA (or, more specifically, Bryke) preferred to tell the audience that Aang is a master airbender without showing us why. I mean, Toph, Zuko, Azula, and Katara are all shown practicing and improving their mastery in bending (although Katara has become rather overpowered), so why can't Aang have the same treatment?
Yes, Aang may be a child prodigy, and he did get airbending tattoos from inventing the air scooter, but I personally think that inventing an airbending technique (which demonstrates impressive ability and skill) is a way to gain the arrows prematurely, but isn't a requirement. Nothing in the show ever suggests just how far he's mastered his native element, let alone the other three. In the beginning of Sozin's Comet, Part 1: The Phoenix King (3:18), Aang says he thinks he still needs to practice his firebending more (which in hindsight makes sense, as he's just started relearning it from the dragons five episodes ago), and Toph notes that his earthbending could use more work too. Right off the bat, Aang is two elements away from complete mastery of all four, but later on he's seen practicing waterbending with Katara, implying he hasn't mastered it either.
We don't even see Aang practicing his airbending by himself post-iceberg, preferring to show off to random girls (like in Kyoshi Island). He just learns the elements, but doesn't really learn the philosophies behind each element. In this regard, he makes Kuruk and Roku look venerated in contrast. (To be fair to Aang, he had a specific deadline to master the four elements before Sozin's Comet that no other Avatar besides Wan had to deal with, but couldn't he try to make an effort to learn from the other nations?) Additionally, compared to Tenzin and Zaheer, Aang doesn't stand a chance against either of them (even though Tenzin is his son, but since Tenzin wasn't the Avatar, he could focus on upholding the Air Nomad culture and legacy). Even Jinora could go toe-to-toe with him at similar ages. He isn't really that impressive in any of the elements, to be honest; we've seen what a master of any specific element can do in both ATLA and LOK, as well as in the novels.
The main thing people often get wrong is that mastery isn't a final goal; it's a specific mindset. As in Pai Sho, what separates true masters from everyone else is that true masters always look for improvement in their strategy or skills. That's why Aang isn't a real master of the four elements: He always takes the easy way out, never trying to better himself or improve what he can already do.
I think this quote from Zaheer perfectly sums up what I've been saying: When you base your expectations on what you see, you blind yourself to the possibilities of a new reality. Even though it stems from his anarchist beliefs, it is genuinely one of the more insightful pieces of wisdom in the franchise because it promotes progress, a constant theme in life. Toph was able to invent metalbending because she wanted to "see" a reality where she could be recognized for her own talent in spite of her blindness; Zuko could learn firebending from the dragons because he could see a reality where he would regain his honor and fight alongside the Avatar, and so on. By contrast, Aang only takes things from surface-level, not putting any effort into understanding the true meaning of being the Avatar.
Speaking of Pai Sho, guess which Avatar constantly improved his/her abilities? Kuruk. Unlike Aang, Kuruk readily asked his companions, Jianzhu, Hei-Ran, and Kelsang, to continue teaching him, ever after he mastered the four elements that he was required to do, saying they would all benefit from the experience (the "true master" quote I mentioned above was actually said by him). Not only that, it was even inverted; sometimes they taught Kuruk, other times he taught them (which technically makes him the first known Avatar to teach bending to others). He was right, as during their lifetimes, they were the most powerful benders of their respective elements in the world!
Kuruk also had an intuitive connection to each of the four bending philosophies, which to this day remains unrivaled by any other Avatar, and was also one of the first people to suggest the idea that the four elements are connected (homeboy's literally a younger Water Tribe Avatar version of proto-Iroh, I'm honestly not going to be surprised if Iroh actually learned his belief from Kuruk during the former's visits to the Spirit World over tea and Pai Sho matches). If you ask me, Mone, learning the cultures and philosophies of the four nations is way more important than mastering the four elements, because the Avatar isn't just the bridge between the four nations; he/she is also the symbol of a unified world, and the franchise is saying that only one Avatar even bothered to do that? In my opinion, if we go by this rule, that easily cements Kuruk as the greatest Avatar in history!
Aang, on the other hand, never does this. Instead, he puts the Air Nomads on a high pedestal (which in turn causes him to place Katara on a high pedestal), and doesn't respect or learn from other nations' philosophies. He openly disrespects SWT culture and actively makes sure Tenzin doesn't have any exposure to the culture that Tenzin still belongs too, and worse, he pushes his own culture on other people's throats (remember the time he forced a homeless couple to "give up on hope because it's a big waste of time"? Or the time he forced Katara to not murder Yon Rha?) and values his own nation and values above the rest of the world (like the time he refused to kill Firelord Ozai because "all life is sacred", even though he has actually killed before, but if he doesn't kill Ozai, the latter's going to burn the entire Earth Kingdom to the ground!). That doesn't sound like something the Avatar is allowed to do, but Aang gets away with it anyway because ... hero?
There's actually another Avatar who focused on his/her own nation above the rest of the world. Avatar Szeto, Yangchen's predecessor, became a government official in his homeland, the Fire Nation. Under his tenure, the Fire Nation transformed from a fragmented, disaster-stricken state to the centralized, technologically-advanced nation we know of today. Unfortunately, this led him to neglect the other nations and, shortly after his death, the four nations were caught in a political event known as the Platinum Affair, which Yangchen had to deal with, eventually kick-starting the cycle of the current Avatar fixing their past lives' mistakes, while leaving problems for their future selves to fix. This problem might have even led to the growing ambition of Firelords Zoryu and Sozin as dictators, with the latter starting the Hundred Years War.
Aang not only valued his own nation's values above the others, he also forced said values on his non-Air Nomad companions; signed anti-miscegenation laws and tried to forcefully deport Fire Nationals from the colonies to return the land to the Earth Kingdom, even though they had already blended in with Earth Kingdom citizens, didn't wan to be separated from their families, and Zuko perceived the citizens of mixed heritage as his own subjects; refused to let his family practice SWT culture, even though his children could benefit from being members of both cultures, not just one or the other, and set an example for mixed-race families around the world; refused to teach Kya and Bumi Air Nomad culture because he thought they weren't airbenders and therefore "not real Air Nomads", even though they were just as Air Nomad as Tenzin was, if not more; and forced Tenzin to uphold the legacy of an entire nation on his shoulders. The fact that this was all written by complete accident is the cherry on top, representing just how badly Bryke screwed up.
... On a completely unrelated note, The Other Side of Paradise by Glass Animals (which is also one of my favorite songs) is definitely a Kuruk song. The last third of the song in particular sums up his tragic journey as the Avatar so well, and I always think of him while listening to it.
