Okay, the "Aang was a bad father" bullshit got me feeling some kind of way, because I think people completely miss what the narrative said about both Kya and Bumi and their relationship with Airbending culture.
Because if you actually pay attention to how the two of them talk about their father and what he tried to teach them about his Airbending culture--they are dismissive about it. They don't care about Airbending. At all.
They can't remember any of the history correctly. They vaguely recall how Aang tried to tell them stuff about Airbending culture. But they handwave all of that history and kind of eye roll it and shrug about it like their father's culture never mattered to them.
Whereas Tenzin remembers all of it. Because he was an Airbender and knew the culture rested on his shoulders (and Bumi and Kya were clearly not going to help hold up that burden.) It mattered to him.
It clearly did not to Kya or Bumi, or they would know more about it.
I mean, the Air Acolyte's don't even know who they are, which tells me Kya and Bumi have engaged exactly ZERO with Airbending culture since they were kids. Why would the Acolytes remember them when they haven't been around, haven't furthered the culture, haven't engaged with it, haven't shown for a single second that they care about it?
It's not because they're not Airbenders themselves. Because the Air Acolytes are not Airbenders either, but clearly they still care about the culture enough to try to preserve it despite having less of a connection to it than Bumi or Kya do.
Not being an Airbender is not an excuse.
But it was never important to the two of them that they engage with the culture. Aang clearly tried to teach and engage with them, as evidenced by the half-remembered bits of history and culture that they DO know, but then I think Aang realized how little they cared--and then gave up and (mostly importantly) let them be who they are. He didn't make them engage with his culture against their will.
Kya wanted to be a free spirit that traveled the world. Okay, do you, baby girl. Bumi wants to be a soldier? Go get, em!
He clearly supported who his kids actually were and didn't force them to be something else.
So Aang did all of those Airbending things with Tenzin because Tenzin cared (and showed that he needed and wanted to know the history and culture) and Kya and Bumi showed that they just didn't give a shit about it.
That doesn't make him a bad father. He let his other two kids be the kids they wanted to be, and what they clearly didn't want to be were Airbenders.
The fact that they grew up and looking back only feel excluded when they think about the fun things Tenzin got to do while exploring Air Nomad culture, but don't feel the same way about the more mundane aspects of it says it all.
They wanted to do the fun stuff, but wanted to do none of the actual work of preserving their father's nearly extinct culture.
"I didn't go on a trip to learn about things I didn't even care about, so that means Dad didn't love me."
Please. Be butthurt somewhere else, because I'm not buying it.