The Legend of Korra didn't ruin Katara's character.
This is one of the many things I've heard others claim for years; that The Legend of Korra "ruined" Katara's character by making her a "housewife" and "the Avatar's wife".
Katara isn't remembered or referred to as either of these things in the sequel series. She may not have her own statue like Aang, Toph, and Zuko, or isn't a fighter like she was in the original series during her youth, but that doesn't mean that she's insignificant.
She's remembered as being one of (if not) the most skilled and powerful Waterbenders in the world and even outlawed Bloodbending sometime after the Hundred Year War, something that Katara is against because of her own experiences with its horror, along seeing that the bending technique is extremely dangerous as it controls others against their own will and wants to prevent Bloodbending from being used for evil purposes.
Not to mention that Katara taught Korra waterbending and healing, encouraged Korra to follow her destiny when the latter tried to leave the Southern Water Tribe compound to go to Republic City.
She tried to restore the rest of Korra's bending (which was permanently blocked by Amon during Korra's final encounter with him), and played a critical role in Korra recovery from the latter's following the events of the season 3 finale by not only using her healing abilities and guiding Korra through physical therapy to regain Korra's strength in her limbs (mostly her legs), but also emphasized with what Korra was going through and was very patient with her, even when Korra snapped at her.
During that time, Katara provided a calm, supportive environment in the Southern Water Tribe for Korra for months, allowing Korra to process her trauma, fears, anger, and emotional turmoil, which culminated in Korra finally being able to walk again.
And what's wrong with being a housewife?
Women can choose whoever they want be, and there's nothing wrong if they choose to be a housewife or a stay-at-home mom.
Also, Katara isn't just "the Avatar's wife" and "Aang's arm candy" despite marrying Aang sometime after the events of the original series, and has never been considered like that.
Even in the original series during her youth, Katara isn't just "the Avatar's girl" and "the beautiful girl/love interest that Aang fell in love with".
Katara is her own character who isn't an object or a prize to be won; both in the original series and its sequel series.