Korra did get into some mature relationship stuff, although it had to be hidden because of the network. If you read between the lines a bit you realize that Korra had a very awkward sexual experience with her first boyfriend, resulting in them breaking up and Korra subsequently finding a girl to start fooling around with.
I think there's reading between the lines and there's "we forgot to write." This was defo the latter.
Bryan even said it wasn't planned. They spend the first two seasons outright antagonistic fighting over the same guy to the point where I'd be more likely to believe Aang and Zuko were secretly roommates than Korra Asami lol. I also don't buy network restrictions, as network restrictions may make it risky to make any overt affection risky, but in much the same way that avatar already showed you you could have killing be a core central aspect in avatar without falling afoul of any restrictions on showing overt killing, and you can already show two characters in relationships with metaphor or symbolism without making them get naked for the audience, you could at least have the two have real chemistry. We got Suki kissing a blushing Toph but couldn't get any Korrasami moments? Ending kiss felt more like fan service than a logical end point X
D
I enjoyed the F. C. Yee Avatar books, I definitely recommend for a more mature treatment of the setting. There are two on Kyoshi and two on Yangchen (I haven't read the last one yet). Appropriately enough, the solutions of one Avatar create the conditions for the problems of the next Avatar, and each of them have their own strengths and weaknesses both with their bending and how they relate to others.
I could never fault the original Aang for being immature; if anything it was one of the most mature kids shows to have come out in history. Overt genocide, imperialism, gender discrimination, industrialisation, concentration camps, government secret police, brainwashing black sites, the philosophy of killing, dealing with the shame of past, kids lost in the world, the way they treated the antagonists Zhao/Jet/Zuko/Azula was so respectful to their pains and flaws. How many kids shows made you feel sad when the villains were crying and screaming defeated on the floor? But the moment that really sticks out to me is Zuko alone and Kitara confronting her mother's killer. In Zuko alone, Zuko does everything "right." He helps everyone who needs help, he puts his life on the line fighting for them. In the end he cannot escape being who he is, and the only choices he has are to die and submit to the world, or exist and be himself. He wins the fight, saves the town, but everyone forsakes him for who he is, not what he has done. He is punished for existing, and for doing the right thing. That was such a cool moment to watch as a kid, gave so much to think about.
Or when Kitara confronts her mother's killer. She is straight up using blood bending, about to turn the man into swiss cheese with ice spikes. She is furious, livid, and in the end decides not to kill him, saying he's just an empty nothingness. Aang tries to console her on the moral correctness of her giving up on revenge and taking the first step to forgiveness, to which Kitara replies she
hasn't forgiven her mother's killer. She wonders if not seeking revenge made her weak, or made her strong. Aang reiterates violence is never the answer, to which Zuko just asks him is he ready to kill his father.
It's all questions! Question after question, with no clear answer. What is right, what is wrong. Who is good, what is good. Aang was like this throughout. Yin and yang, within yin there is yang, within yang there is yin. Every nation, every element had its evils and joys.
Korra meanwhile has clear right and wrong, Vaatu bad, Raava good. All of the moral problems are resolved without addressing their root issue, with the whole problem resolved usually due to a successful violent struggle. Equalists are nullified through violence and the hypocrisy of the leader. The clash between Lin Beifong's duty vs Suyin Beifong freedom is resolved when Suyin beats Lin in a fight. Unalaq spiritualism vs the avatar & the republic's materialism is resolved because Unalaq is allied with the bad spirits, Korra's fighting for the good spirits. The underlying issues that led to Zaheer's anarchism or Kuivra's authoritarianism again aren't really addressed. It's just to the victor the spoils. The stuff with the Earth King at the end being put back into power only to willingly abolish the Earth Kingdom in an offhand comment was like woah. Dude abolishing the Earth Kingdom could be its own four season show.
And then there was this rat's fart jokes. I felt like we went backwards with Korra in a lot of ways
*EDIT
I feel the need to just add at the end, I actually did like Korra lol. Don't want to sound like a hater
*EDITx2
WHAT DID YOU DO KORRA?