Downsizing is a film with the most brilliant premise. What if, to save the planet, we were all made tiny? What if we only took up a tiny amount of space and flew in tiny planes and produced tiny amounts of rubbish? And what if we could live in the sort of mansions that would cost millions if they were regular-sized? What if, what if, what if, what if… but most crucially: what if this film had run with the premise rather than throwing it away? Could it have avoided becoming just another dumb ‘white saviour’ movie? And this, alas,...