Mirabel first comes in introducing us to her family. She seems so proud of them all--but gradually we realize that she is too perfect of a poster child. Beneath Mirabel's proud words is her great pain at not having a magical gift like everyone else in the family. She has this grand idea of her community but not of herself. She think she is the only one who has nothing to offer or who has no acceptance--which is why she tries even harder to be that poster child of all that is wonderful about her family.
But over time, Mirabel realizes that she isn't the only one who has feelings like this. Her sisters Luisa and Isabela are both breaking into the pressure of expectations. They also don't feel loved and accepted for who they are: they feel like their value is in direct response to what they do to serve. Her cousin Dolores lives under the pressure of keeping family secrets, and Dolores's brother Camilo is literally always shifting identities. Only Antonio, as the youngest, seems to still be untouched by the family drama. Note that his gift is to talk to animals--that is, to communicate. Communication is what the family as a whole needs to learn.
Take Pepa. Her emotions affect the weather, so she is always trying to stuff down her feelings. But pretending issues don't exist is never very helpful towards problem solving, is it? Instead, the different memories of the family need to learn to be who they are personally and then within the group. No stuffing issues.
Mirabel admits her pain. Isabela admits she is living a life she doesn't want--even getting engaged to a person she doesn't want to marry. Luisa admits she can't do it all. And their grandmother admits that she has been controlling the family too much and pushing them to her idea of perfection instead of simply loving the miracle of their survival. Mirabel was "rejected" by the house when she wasn't given a gift--but the first rejection was when they pushed Bruno away because his gift couldn't be controlled in predictable ways. Bruno's reunion into the family shows acceptance of that which is unpredictable and even imperfect.
So when the house "left out" Mirabel, it forced the family to remember the family members rather than just their gifts. And it forced Mirabel to ask questions and bring to light the individual hurts and start a conversation. Mirabel sees that her identity isn't formed by her lack of a gift anymore than her sisters' identities are based on the gifts that they do have. And so she has a better idea of herself and of herself within her family. Both the individual and community identities experience wholeness and healing.