People who think it sucks are either bandwagon faggots who are only saying it because other anons have said it before, these are the same people who usually spam One Piece threads with "Set Fail for One Piece". Or, they have never experience anything that any other characters have so they don't understand their motivation. These are the people who ask question like, "Why didn't the faggot just give her letter?" "He should've just sent her the messages, the pussy." "Why didn't he just run after her at the end?" This can also be explained by a total lack of empathy, which a lot of people on 4chan have. But there's also people who say it's the best thing ever partly because of bandwagon faggots and others are blinded by the cloud porn and think that the use of voice overs automatically makes it meaningful.
It's good, it's damn pretty, but the writing gets old. Shinkai can tell a story without the use of words and it's great. He's one of the few directors that doesn't mind showing you something rather than telling you. But here he fell into a trap, he's trying to tell a story of three character's distance between each other and if they're distanced it's hard to develop the story with dialogue alone and no internal communique.