>>718361271
>B-But their parents didn't appear later
Brother, we already knew before their parents showed up they got their powers from their parents. Why does this need to be explained to you? We knew people who have special jutsu that can't be copied by Kakashi and other Sharingan users or just flat-out moves that can't be taught came from their bloodlines. Kekkei genkai ("bloodline limits")
>So, as Kaguya was never stated to not exist, her existance wasn't a retcon.
No. Why do you think she is a retcon? Again, retcons are something that is stated, and then they are changed later on.