This is going around so let me talk about world building. During Aang's time, all four nations were isolationist, they didn't mingle until the defeat of the Fire Lord. After which, Benders now were trading openly, interacting peacefully and intermarrying. It's increasingly common to have children now with different element bending. And with metropolises such as Republic City under the rule of no singular bending related nation, only increases exposure to all four more. Now, children in real life learn through mimicry, copying what adults do because every kid wants to grow up and be independent. They require adults, though, to fine tune and improve these skills, but they can learn basics on their own. Pavi and Nisha are in a unique spot where the apocalypse happened. We know massive destructive storms happen all the time and it's the Avatar themself that is blamed for it (obviously setting up so it was Korra that actually saved it). No adults can be trusted, you will be hunted down and possibly even killed if you reveal yourself. So naturally, you do your best to improve what you can by copying adults. And now that bending specific nations are no longer a thing, it's easier to see observe how people use the elements. Pavi and Nisha are also shown to not to be the best. They imitate Jae to improve their air bending to fight the storms or save the camedillo. Other benders who know their secret are also training them, with Nisha being far more obviously trained (by 3 years) than Pavi. I get people want to find things they hate on the show because it's the new show. And some racists are going to hate Pavi and Nisha entirely because they're dark skinned girls. Every show isn't and shouldn't just be "Aang's story but with a different mask". Korra, Pavi and Nisha all exist in different periods of history in different geopolitical (and in the new show's case, geological) periods in time. Showcasing out of context clips, while pointing and saying how awful it is isn't really critiquing, it's just cherry picking.