Japan is in a damned if you do, damned if you don't position with this one. There aren't enough women interested in Sumo Wrestling to make a worthwhile female Sumo league and Little Miss Sumo can't compete with the men. If Japan allows her to compete with men in order to appease modern feminists, then those same feminists will only complain when she is defeated in every match.
I think the big message from the film will be one that a lot of people miss: Accept the cards you have been dealt and play to your strengths. Don't waste your entire life chasing dreams that you have no hope of realizing.