This puzzled me. I read it again. Yes, this person is angry that the story ends in sadness. Why, this is the whole point! This story, albeit fiction, is depicting life as it is. Not as it ought to be. This is writing! Writing with talent, with skill, with emotion and aesthetics all at play. This is moving the reader, moving the world with words alone. This is the heart of literature; what it can do and what it should do! Move something, do something, be something all on its own by its own heart.
As I have mentioned before, this is what great literature does. It changes you and it stays with you forever. Even in the maelstroms of my very busy life, part of me is still sitting silently with Marie-Laure on the secret beach feeling the water slip back and forth over my bare feet, touching the world she will never see. Part of me still cries for the loss of the world, for the cruelty and the people pushed by fate to live in fear and longing.