I've said it before, it should have been at least pg13. At least.
They could have really explored the Isle and the effects that living there had on those children, along with the things they've gone through. Because it is an interesting concept. Here you have all these villains who have to live on this island. They're going to feed off of each other, a lot will probably get worse.
And the kids. In the books its played off like its not a big deal, but they don't even have decent food to eat. They definitely have to form gangs for their own safety. There is going to be rampant child abuse, there are going to kids doing whatever they can to survive, to get food, to have shelter. There are likely going to be teen pregnancies, and more deaths for all ages than any of us want to think about.
And the island politics! The magical people, the pirates, those who are neither. How about Frollo? There is no possible way that he is going to be the only one fully against magic. While Maleficent might be able to escape harm, you can't convince me that even Mal as her daughter could escape it. There are just too many people on that island.
And the size of the island! I'm certain its bigger than what we think as it sounds like people are just... sent to the Isle for even minor things.
Along with the Isle, it then makes you want to get into the politics of Auradon. What really led to the Isle, how all the stories and times merged, which heroes were for it and which argued against it. What about the corruptness? What's really going on behind the scenes of what were shown? I mean, a sixteen year old is becoming High King! While his father is alive and still in good health! (Unless he's not and we just weren't told...) That's very suspicious.
Honestly, this franchise could have been dark, gritty, and pulled people in. Instead, it was watered down so they could sell it to kids likely in hopes that they would make more money. Still fun, still nice to play around with for fanfics, and great music. But it could have been so much more.