Well for one, it's really not 'fixing' she needs; rather it's just character development. Her personality itself is perfectly fine; she's not your stoic, cold faced badass female character who is also a bitch to everyone (let alone female knight) which we see way, WAY too often written. She's warm, kind, humble, can be hilarious (her cooking, fear of bugs, bad sense of direction, people making her flustered, her love of cute things) on top of being a badass.

In saying that, you do have to squint very hard to see some of the character development Katalina has got (and put pieces together as well). Much like how Vira's is locked behind her character fate episodes, Katalina's is locked behind main story quest (and in turn, that's why we've not got anything about her family etc. apart from knowing Ares is her ancestor).

The first character development she got is in fact in plain sight; the Albion arc. Katalina was held up on her guilt over what she did for Vira for all of the 6 years she served Erste. I also reckon that it was one of the biggest if not biggest pushes for her freeing Lyria other than the vow she made to the girl; Katalina was not about to leave another person she'd come to care about trapped in a cruel cage, especially when the one she had left, she was responsible for trapping there. In a poetic turn of events, this same girl she freed is the reason why she was able to free the other and undo the damage she had done.

The next facet of character development is how she's slowly and steadily over the years (and literally in years) let go of her anxiety and nerves over Lyria. Even Sawashiro Miyuki mentioned this in her message at the 10th anniversary stream to us of how Katalina was letting Lyria go more and would start to think more about herself, Vira and the other important people in her life. What Makes the Sky Blue and What Makes the Sky Blue II show more of Katalina letting go of Lyria more.

The most hidden detail of Katalina's character development is actually in her innermost teachings with Ares. It's hinted Katalina does not love herself and has low self-esteem for all her pride as a knight and confidence she outwardly shows when Ares outright tells her "You should learn to love yourself." as her parting words. It's also revealed Katalina was not prepared to accept the responsibility of great power and wanting freedom and to be a knight aside, that's another factor into Katalina's leaving Lord Commander to Vira as well when you look at it.

GBVSR also shows some facets of Katalina; one particular moment is in her win quote against Anila where she says she sometimes feels like she's cracking under the pressure of defending the crew. Even Katalina can only stay so strong and needs support (Lyria, Vira, her fellow main crew members etc.).

But to straight answer your question; I absolutely agree Katalina deserves more and better. We need to be able to delve into her family (especially now that there's an ancestral link to Ares) and even more so; she and Vira together need their own story event, addressing both of them and also Ares and Albion (we really need to find out just what killed Ares, an almighty Astral General known to be regarded highly in strength and tact even among other Astrals). Let alone the fact that basically, both Katalina and Vira have Astral blood in their veins confirmed and thus far are (to my knowledge) are the only characters confirmed to have such (which kinda makes them Astral-Human hybrids; Vira becomes an Astral-Primal hybrid when she becomes Chevira). So where does that put them on the power scale to everyone else considering Astrals are like, only below the Omnipotent and Lucio in power scale (and on par or possibly stronger than The Supreme Primarch).

But I am hoping that after the last MSQ update and where it seems to be going; we are in fact, finally going to get all of what I mentioned above; and Katalina will not only finally get more and proper character development but alts as well (and the same with the rest of the main crew not named Rosetta getting alts).

Apologies for the long arse answer anon, but thanks for asking!