I kinda feel that this movie is kind of overrated. It doesn't have any message and the only thing that really sets it apart from romance in other anime is that it's presented in a realistic way, which is actually far easier than writing a decent fiction.
People need to get over the idea that 'realistic' writing is some sort of achievement compared to a thoughtfully abstracted derivative of reality. Are Shakespeare's plays a realistic representation of interpersonal relationships? No, because he wasn't a hack writer.
In any other medium this story would have been considered mediocre trash, but because it's a little unconventional in anime it's lauded as the anime equivalent of the Mona Lisa.
Seriously, fuck this movie, fuck the stain it's left on anime and especially fuck everyone that uses it as an example of anime being 'art'.