I don't disagree with this
I don't entirely disagree with this either.
I think this is a very simplistic way of framing the counter argument.
Overall the truth is somewhere in the middle, yes asking for help is not a sign of weakness at all, but the context is important. Namine, Xion and Aqua have all had good foundations for their character, and two of these characters have even had concluded arcs (Aqua was right at the end of hers but not quite there yet). I would absolutely argue that even in KH1 and KH2 Kairi was a decent character and we got a glimpse into what she's like and her motivations. However that's not KH3. All of these characters had their best showings in games that weren't KH3.
Namine was reduced to one missable cutscene where only her voice was heard. Xion was used as a pawn for something that was totally opposite to her motivations as a character, and now that we know it was Xion from shortly after her birth who was a nort, it makes even less sense. Aqua was treated absolutely terribly in KH3. After all that time in the realm of darkness what reduced her to becoming influenced was....a mega dark ball of darkness and destruction. Nice. Okay, so at least she gets to fight Vanitas and help Ven and-oh. She lost. Even though she's beaten Vanitas plenty of times as a much much *much* weaker character. Even if she was tired, she should have been leagues above this Vanitas who had come from a time prior to his last battle against her. Nothing wrong with asking for Sora for help but she shut Sora out, this should not have been the time for her to suffer something so embarrassing. Kairi....was Kairi.
Point is, all of these characters were done dirty in KH3, it's not about whether asking for help or not is a bad thing, don't latch onto the small things in people's arguments, it's about whether these characters were done justice, and truth be told anyone not named Sora was not.