In an ideal world...(spoilers)
...Nader and Simin would have reached a compromise regarding their marriage. I wondered why the possibility was never even broached of Simin staying to care for his (after-all) very elderly and frail father then later join his wife and daughter overseas. That way, Simin could honour his father, keep his marriage and his daughter would have the start of a possibly better future.
I felt so bad for the daughter at times that I wanted to slap both of the parents. I nearly cried. I think she reminded me very much of one of my own daughters (soft-hearted and kind) and that's probably why.
I also thought that Simin really kind of owed the woman some form of compensation as after-all, had she not lost her in-utero child chasing after his father to save the father from being hit by a car himself? At some stage, I was annoyed with every character, except the daughter and the elderly father. But they were all in these very difficult situations.
Inadvertantly perhaps, the film says a lot about the importance of mutual co-operation and respect for others, by dint of a general lack of these qualities having been portrayed.