See, I do agree that Kiara did salvage herself somewhat because her "Phoenix warrior with terrible shield and sword" design was the least interesting of the 5 girls. The KFP thing is the most interesting thing she did but I still find it a really boring gimmick. It's just the bland "All my viewers are forced to do what I say" thiing. Loads of other girls did that long before she even debuted.
I don't like Kiara because her entire bit seems to be flip-flopping around between things. Debuted and was boring? Okay, well, now she's a super lesbian obsessed with Cali which was just cringe. That didn't take off as well as she expected because Cali got so popular on her own? Okay, well, at least I'm the only one who can speak Japanese fluently! Oh... that just annoyed my fanbase when I tried to shoehorn it in... well, now I'm the "fan girl" stereotype obsessed with Pekora. Okay, that kinda worked but after I met her, it burnt out quickly. Now I run KFC. Okay, that didn't really take off. Well, now I'm a talkshow host with the Japanese girls to leech off their popularity. Well, that burnt out surprisingly quickly... Okay, now I'm a dictator in charge of KFP forcing my viewers to work for me. Okay, that kinda worked. Well, now I'm the "head" of the Holobirds, because I'm the 3rd most popular of the group (despite being the number 1 in subs), but at least the 1st can't even speak English so poor Subaru has to awkwardly sit in the corner during collabs.
I have no idea what gimmicks she's still doing at the minute or other gimmicks she was bouncing around doing between the ones listed above. I think she's got the weakest "gimmick" and personality as a character and if someone put a gun to my head and told me to name her gimmick, I'd say it's just leeching off other members. She's the one always trying to do off-collabs to get fan art made. She's the one who has most heavily connected herself to her iRL persona. She was desperate to be the first to collab with as many JP talents as popular. She tried to force herself into the popular Pekora/Moona pairing when that was huge, the second it burnt out, she lost interest in it entirely.
Ame's lore and personality did change a lot so much so she's probably my favourite of Myth. Cali's did too but Cali's first personality of being kind of awkward and weird just didn't work for me, her 'I'm a cool boomer dad chad' thing also doesn't really work at all for me. Gura has been pretty consistent from what I've seen. Ina, I haven't watched a lot of because she's just 'fine' to me. Not one I've ever wanted to seek out to watch but not annoying like I find Cali can be or Kiara just is.