As a kid I really got into Legend of Korra when it debuted, but as I kept up with the story my feelings go all over the place. While it doesn't exactly ruin the franchise, I mostly have issues with what's going on in this series. For starters, Korra is an okay protagonist. The idea that she can manipulate three out of four elements at a younger age than Aang did is impressive. Unfortunately, she is no Avatar Kiyoshi in my eyes. It's not that she is not as in tune with Airbending as Aang was, it's that she had many more points of weakness compared to others. One time a few times it puts her in a weak mental state, other times she gets into physical sickness, and worst of all one of her fights managed to do permanent damage. And speaking of, Korra has only used the wisdom of her past lives about one time only, and it was in the most controversial season.
Korra as a protagonist is not the only thing I have issues with. The writing is also an issue. There are so many missed opportunities and potential moments that could have kept the previous series alive. For example, it is clear that Korra is the reincarnation of Aang, but he's only interacted with Korra twice. Aang had more interactions with Avatar Roku. Heck, both Roku and Kiyoshi had more screentime in The Last Airbender than Aang did in this series. Another thing that could have shined some light on would be what happened to Sokka and Suki. It would have been cool if Korra turned into Aang like how Aang turned into Kiyoshi during one of the fights with Unalaaq.
Flaws and all, the show does have some good things. Desna and Eska were good side characters in season 2, despite Eska being a toxic girlfriend to Bolin. And speaking of Bolin, he's kind of like a reincarnation of Sokka in the form of an Earthbender with the childishness of Aang. I also like Asami as she shows how Non-Benders can be strong fighters. Overall, the series is just okay, just be prepared to get some tissues, you'll get your heart broken more times than in the last series.