You described my irritation with this book better than I could've. Yes, EXACTLY...it was heavy-handed and the characters were annoyingly precocious and I just...couldn't, though I *did* make it to the end. I wanted to love this book and be utterly enchanted by it and I wasn't. I considered reading the sequel but after your review, I think I'll pass.
To be clear, I *did* finish The House on the Cerulean Sea, but I had checked the sequel out of the library...and it felt like...it would be a chore, and I dreaded having to start it, so when The Story Graph had "animal death" and "animal cruelty"...I was like "oh, GOOD, a great excuse not to read it" and returned it unread.
It's just...overhyped mediocrity.