Again, in case you missed it, he is 15 years old and she is 25.
Imagine if the genders of the two leads were reversed. A 15 year old girl falling in love with a 25 year old man and in the end she gets him. There would be outrage. It would be cited as typical male oppression of women. People would say the movie is exactly what is wrong with Hollywood. It would be viewed as sexist. It certainly would not have won any Oscars.
Why is that true? I think the best explanation is that our society is so fundamentally sexist we believe deep down in our collective conscious that a 15 year old boy is more responsible than a 15 year old girl.
Same reason we believe a woman who divorces a man to be with someone else, refuses to contribute anything to the upbringing of the children yet is able to make just as much as him, ends up with lifetime alimony. It would never happen if the genders were reversed. Which is precisely the reason I am so in favor of equal rights.