I agree with you honestly, and that's part of why current-day Moon is more appealing to me now after all: we've actually seen her accumulated problems across the series, knowing she's lived years worrying about her kingdom and Star and having to take on a persona she may still not feel ready for, while in the end young Moon really was just a cute kid up until what we saw in the flashback
before then though, even before her involvement with Toffee was confirmed, I remember the sense of mystery/excitement about seeing a younger Moon for the first time in the comics, and of course even more so after her tapestry. the question of what must have happened to turn this young girl into a warrior, what crazy stuff happened in the years in between, and all that.
now we know the answer, and it's maybe not quite as extreme as some predicted despite being more extreme in others (all the Eclipsa stuff). as in her not being an adult warrior fighting a climactic battle, but a child Star's age in a bad situation trying to find a solution. and I really do like that the tapestry was a total dramatization, and even that by now Moon feels like a totally different character than I used to believe.
it's just now I that I know what Moon went through pre-darkest spell, there's no longer the question of what changed the character from the comics: we actually saw that moment of change, the innocent/cute art of her no longer has the mystery of what happened to her later around it
but I really do like that the slow revelations about Moon's history at first leads the viewer along the same line of belief as Star before it gets shaken up for both at the same time