Headcanon with literally no evidence to back it up alert.
Also long post that avoids the actual question until the very end alert.In the older series, we were told cats are in StarClan in whatever form they feel happiest in. So Longtail is able to see because he likes being able to see. Yellowfang is an old grumpy hag because she's happiest when she's miserable. A lot of elders who died aren't their old, graying selves (other than Yellowfang), but their younger form where they're able to run around and hunt easily. So I believe when you die, you can choose whichever form your living self had that you like the best.
When it comes to cats born with their disabilities, I really don't know. I don't know if Deadfoot has his twisted paw in StarClan or not. If he doesn't, that means StarClan can heal disabilities. If he does, that either means they can't, or they can but he's happiest with his paw the way it is (which actually makes a little bit of sense, if that's all he's ever known, why would he change it?)
Jayfeather's irrelevant because we already know he can see StarClan's hunting grounds, so eh.
So when it comes to the question of young cats who don't have many forms to choose from, it may be a similar thing to cats born with disabilities. If you have to pick a form your living self had, then it makes sense we'd see kits and apprentices. If they can choose something else, there's so many possibilities.
1. My favorite is the idea that kits won't age until their parents die and are able to raise them. As a parent, it would be fairly upsetting to see your child all grown up without any of your input whatsoever, so maybe StarClan places a hold on their development and they remain kits until their parents are able to be with them. (This doesn't explain Mosskit though)
2. Another one I like is that kits can choose to age, but they don't. Think about if you were a kid, and could choose what age to be. But the catch is, you have the same amount of knowledge and training regardless of the age you pick, and most importantly, you don't know what it's like to be older. Change is scary, so maybe the majority of kits think "hey, I can have all the training and knowledge of a warrior, but remain my playful little self and be cute for all eternity". From an older perspective, yes you wouldn't want everyone taking care of you all the time, but to a child, maybe they don't want to grow up because they don't have any idea what it's like. I'm sure some would want to, but if it's a rare occurrence, we wouldn't see it because the story is focused on 10174 other plotlines and just doesn't have time to discuss it.
3. Perhaps kits do age, but much, much slower than normal. Maybe there's something about the afterlife that keeps them young for a long time even if they want to age, similar to young warriors staying that way for a long time. If cats eventually fade away, maybe a kit who died at birth can only reach the development of a 12 moon old by the time they fade away. This is by far my least developed idea and I'm just talking out of thin air, but it is interesting.
As for the question of whether it's fair or not, it depends on which one of the possibilities I discussed (or one I didn't!) is the case. If they can choose to grow up, but they don't want to, then yes, it's fair. I would also say if they're kits until their parents die but then they age or choose to be their happiest selves (maybe that's what Mosskit did), then it's still fair, they just have to wait a little bit longer. But anything where StarClan is keeping them undeveloped forever without the kit's choice is unfair.
Though maybe it's not StarClan's fault. We know there are forces beyond StarClan, maybe forces that aren't sentient, but just how the universe is. In that case, it's still not fair, but also not really something that can be changed.
I don't think we'll ever know for sure. StarClan is already massively inconsistent between arc 1, arcs 2-4, arc 5, and post arc 6, and I
highly doubt the editors think about this in anywhere near the amount of detail we do. They likely just haven't considered the effects of being young forever, because they're thinking about it from the parent's perspective (Bluestar, who never got a chance to raise her daughter with her mate, is likely happiest having a child forever; Squirrelflight's experience in StarClan is much more dramatic if she sees her kits as they died rather than grown up). So really, there's no telling what's the case for sure.
But yes, if the kits can't choose to age, it is unfair.
