Endings reveal a lot about the overarching ideas of a piece, and by finishing with Korra and Asami, the writers establish that The Legend Of Korra is a story about women first and foremost. It’s a series about how women relate to each other as friends, family, and rivals in romance and politics, an idea has became especially prominent in Book Three. Before that, there was much more emphasis on Korra’s connections with the men in her life: her father-daughter dynamic with Tenzin, her romantic entanglements with Bolin and Mako, her conflicts with Aman and Unalaq. Those relationships made Korra’s experience especially relatable to the adolescent females in the audience dealing with their own father drama and boy drama and the oppressive reality of living in a male-dominated society. But then the show stopped being about that.
The amount of time spent on Jinora, Asami, and the Beifong women in Book Three shifted the focus to the female cast, and Book Four pushed the men even further into the background by spotlighting a female villain and devoting more time than ever before on the inner workings of the title character. There are multiple times in this season when all the major players on screen are women, which is a remarkable thing in any action television series, animated or not. With so much emphasis on the female characters, it makes sense that The Legend Of Korra would end the series by looking at Korra’s relationship with another woman, and just the hint of a lesbian relationship is an extremely progressive step for an animated series geared to a younger audience.”
— Oliver Sava, in his review of the finale for the AVClub.