In the first scene of the show, Korra is set towards the objective of getting in touch with her spiritual side. The crux of the Avatar's spirituality is drawing on the knowledge and powers of her past lives. At the end of the show, she attains the Avatar State, where she can draw on the knowledge and powers of her past lives; it is the successful end of the longest-running conflict of the season. Having done so, she is able to solve a problem of extreme personal and global importance that only one of her previous incarnations had the ability to deal with. It's quite a neat storyline.
If you're saying that it would have benefited from taking the time to make her spiritual progress more explicit or further establish the capabilities of Aang's spiritbending, then I agree. If you're saying it shouldn't have happened, then I don't.