A spectacular show with action, comedy, and heartfelt moments. the main character, korra, learns so much about herself and the world, it is impossible to come out of watching this without having a love for her growth and development.
Where ATLA excelled in creating a traditional/ancient like element, i thoroughly enjoyed the writers ambition in creating an industrial city in LOK. teaching kids subtly that technology develops especially after a time of war is a very realistic approach. not only do the more "traditional" styles become more "modern" like in fighting styles aka bending, but in cities like zaofu they use bending to create new art/dancing. its just thoroughly a magnificent look at how the world of ATLA would look 70 years in the future, it still has its magic but a new age = new themes. and some critics dont do very well with "new".
Just by looking at the soundtracks, ATLA had more use of asian instruments, and Korra kept the asian instruments but the soundtrack is clearly more refined and has a steampunk personality. I would call Legend of Korra a masterpiece on its own not to be compared to ATLA. the show was well ahead of its time and i expect people to come around and realize it does not deserve even half the criticism it gets