On some level, it's not as unenjoyable as "Ponyo", so it's got that going for it, at least.
The basic premise of this story - that the protagonist doesn't understand what a subsidy is or how to use Google - is central to why I find this film incredibly moronic at the best of times. She knows what a sanitorium is, but not a subsidy for adopted children. On one level, she is a child, there are concepts she's not necessarily going to understand just yet about how the world works. On the other hand, she has access to the Internet and isn't using it. And didn't just... talk to anyone about it. At all. I mean I love me a good miscommunication plot, but this one's just kind of silly, particularly since she is on some level intelligent.
What's also very silly is this isn't even the only twist, and I can't really decide which is worse. I'm not mad there's an incest subplot or even fully that they queerbaited the story in the various ways they do it. It's lazy and I expect nothing better at this point from a Ghibli film. If you want very pretty friendships and straight romances, Ghibli does it like nobody's business, and that's fine. I absolutely love several of them, particularly "Princess Mononoke", "Howl's Moving Castle", and "From Up On Poppy Hill". Marnie, however, is unsurprising, but also quite boring. It's an odd "you thought we were being revolutionary!" gotcha that's so overly complicated yet somehow lazy, badly written, and just plain ridiculous.
It's a pretty film. If you step away from the stupidity, the story about two girls who form a friendship - and perhaps one-sided romantic attraction - is quite sweet. It's still not even remotely as enjoyable as most of Ghibli's better films. I disliked "Tales From Earthsea" less than this film. If you want animated queer relationships, watch yuri, any number of shoujo, boy's love, "Steven Universe", "The Owl House", "She-Ra and the Princesses of Power"... anything that's not this.