It's a socially weighty and very worthy movie to make in the MeToo age, but while I'm a big fan of Sarah Polley as an actor and director, there were too many things that kept it from being great.

The script is based on the true story of a remote religious community in South America where the men had been drugging the women and raping them in their sleep. The community in the film looks Amish, but neither the location or the faith the locals follow is revealed.

One day the women of the unnamed colony meet in a barn in secret. They all know what's been happening and have gathered to decide – in quite studious and officious fashion – what to do about it.

With their meeting taken down as notes by the kindly colony school teacher and the sole man who seems sympathetic to their plight, August (Ben Wishaw), they run things like a court proceeding as they try to figure out whether to stay and put up with the abuse for want of anywhere else to go, stay and stage a battle they're unlikely to win or take their littlest kids and leave the colony.

Opinions and feelings vary, from the prickly, reactionary anger from Salome (Claire Foy) to the more level headed Ona (Rooney Mara) and everything in between. Some want to vote, some want to kill, for some – like Mariche (Jessie Buckley) – it's more urgent than ever with a drunk, violent husband at home.

It's telling that the men in question are never shown in the movie, echoing an early sentiment that the women are told they've been attacked in their sleep by ghosts, their aggressors obviously counting on them all being too illiterate, sheltered and superstitious to know any better.

But the premise itself seems damming of the world and the way society has traditionally treated women – the very existence of their discussion and the paths they might take highlighting how little recourse they have.

One of the biggest drawbacks is the visual. Polley had her DP wash almost all the colour out of the picture to represent a world that had faded for the characters, and even though that's a legitimate creative choice it makes it all very visually uninteresting and flat. And because the story itself is about people talking (not that the title didn't warn you) more than taking any particular action, it makes it more a manifesto than a movie.

The movie itself also seems to take Ona's point of view – very stoic, matter of fact and systematic even though it's about something so emotionally charged and morally abhorrent, and it comes across all a bit didactic.

We also don't find out until partway through that it's actually set in the present day when a census van drives through the community exhorting people to come out and be counted and identified. I thought until that point it was in the pastoral era of the 19th century or something, and while it shouldn't matter when it was set and the crimes committed would be no worse in another era than they are in ours, it's less forgivable today when everyone – no matter how uneducated – should know about their right to legal justice.

Salome and one or two other characters (Frances McDormand, who produces, plays a resident equally as vehement as Salome in the other direction – that they stay, shut their mouths and count their blessings) bring rousing anger and female rage to the screen, but everywhere else it's all just a bit too quiet and subdued, keeping its ankles tightly crossed and not raising its voice where you wish it would.

If you wanted to be really uncharitable you could dismiss it as 12 Angry Women, but the strength of the idea deserves attention even if the film doesn't live up to it completely.