Maybe it was that despite having three strong female leads, the film fails the Bechdel test - all the dialogue shared by the women ends up revolving around the male characters, even though they are very much in supporting roles.
It might also be that all the women are in some way dysfunctional because of motherhood and social expectations around having children.
It could be because of the many plot holes that stretch the willing suspension of disbelief to the limit. Maybe.
Actually, for me it was the first two points that really bugged me (I cope with plot holes in most films and TV series reasonably well - otherwise I would never be able to watch most dramas!). Spoilers ahead for those who have neither read nor seen the film!
Movies that are about women being badly treated by men should, in this day and age actually be addressing the causes of that abuse, not just accepting it as an inevitability and giving the women the let out of a bloody revenge at the end. In the film, the reason the women were reduced to mere appendages to the men was the issue that was not adequately explored. The book, apparently (I have not read it yet) addresses the fact that the women are trophy wives for successful men, despite having their own careers and skills and that their whole identity and purpose is tied up around their ability to produce offspring. However, early on in the film one of the main characters observes bitterly that the whole suburb where the action happen is 'one big baby farm'.
This is the issue that the films never quite gets to the heart of. How much our culture still only values women because of their ability to reproduce. Rachel's real pain because she not only cannot have children, but has been replaced by a new wife who has given her ex-husband the child he wanted, is compounded by the expectations of society around her. Megan's grief over a lost child and her husband's pressure to give him a family that can only remind her of her awful loss cause her increasingly dysfunctional behaviour. But why the culture around these women sees this as their only value and purpose is never challenged.
The Bible has several stories about women facing the pain of the childlessness, and the social disgrace that went with it - Sarah and Rachel in Genesis and Hannah in 1 Samuel are obvious examples. However, God eventually gives them all children, There are no stories about the women denied the chance to have children or who chose not to, so we have to address those issues from elsewhere in scripture.
So what of those who cannot have children. And why is it just the women denied children who suffer - what about their husbands? It seems to me that our culture, including our churches makes the ideal of marriage and parenthood, especially motherhood, a dangerous idol. It leaves those not able or not willing to have children on the edge, left out of social gatherings and conversations that revolve around parenting. For those of us who are parents, the struggles and challenges of parenting occupy our time and energy so much that we are often blind to those around us who are left out.
For women though, the sense that one is only validated by being a mother is a toxic pressure. There is already the ludicrous notion that a woman can only be validated by a romantic relationship with a man. Then, once that man is found and domesticated, the only role left is to become a mother.
The bible does place motherhood (and fatherhood) in a place of great esteem, but Paul points to a higher calling that may lead women and men to eschew such a role, and Jesus himself gave hope that those denied biological parenthood can become mothers (and fathers) to many by other means. Marriage and parenthood matter, but they are not all there is to our humanity and value, and the more we hold on to the truth that there is more to us than our reproductive roles, the saner (and happier) we will be!