I thought that Korra reaching the Avatar State made perfect sense and I’m tired of grr posts so here is my contribution
Aang only reached the Avatar State when a) he was in grave danger, and b) when he could accept that he was the avatar. His Avatar identity was something he ran from, and had to come to terms with in order to control it. Korra was the opposite.
From the beginning of the season Korra defined herself by her Avatar status - kind of like Zuko and his honor. Other characters we’ve seen had greater depth in personality and interests. Think about Aang, Katara, Sokka, Toph, Iroh, Bolin, Mako, Tenzin, etc. All these benders had something outside their abilities that defined them in a greater way. Korra wasn’t like that until the end; she was the Avatar; a fighter; triumphant; indestructible. She closely resembled Zuko or Azula in that mindset.
When her bending was taken away, she felt that meant her identity was gone, too. Just as Katara called it, her “connection to the other elements is severed”; that was all Korra knew from infancy. Bending, bending, bending. Mako tried to reassure her that being the Avatar wasn’t the reason for his affections, but she was still in denial. She had no self worth anymore.
When she cried on the tip of the iceberg - probably near where Katara found Aang omg my creys - she was certainly in touch with her spiritual self! She didn’t have her bending or ferociousness to lean on. She was helpless, just like after her first encounter with Amon and she had a vision of the Gaang.
I think when Korra had to be a person, not just the Avatar, could she sit there and realize the momentousness of the world (as symbolized by her tear falling).
That was the first time she couldn’t use any amount of force, fighting, or even patience to solve the situation. Aang shows up. She sees the other Avatars. She is given her bending; she defines her abilities, not her abilities defining her. I think the combination of understanding, appreciation, and helplessness opened the door to the Avatar State; not when she accepted her Avatar title like Aang, but when she understood the duality of spirituality and humanity - both in and out of bending.
Anyway I think that will be the setup for season two. When she first got to Republic City she got pissy with the protester saying how “bending was the greatest shit ever wtf you talkin about”. Now that she has felt that separation from bending, in a way that reinforces her humanity (and thus her spirituality), can she return to Republic City and work with non-benders. When Mako, Asami, and Bolin were arrested, the non-bender lady yelled out “You’re our Avatar, too.” That sentiment isn’t going away with Amon; Book 2 is around the corner.
So yeah, I call bullshit on lack of character development.