Oh lord I'm so sick of that vacuous saying. I'd love to track down the originator of it and go full "WELL, ACTUALLY" on them.
It's such a stupid saying. And people repeat it mindlessly, without any thought for whether it's true or not. I think that's what makes me so angry, because if you even spent two minutes thinking about it you'd realise it's not true.
I mean, take one of the simplest examples. The 1974 Sex Discrimination Act ended quotas to medical schools. Up to that point, medical schools applied quotas limiting the number of female students. It meant that large numbers of mediocre males took places that should have gone to bright women. But once the quotas were stopped, women flooded in, taking up the places, so nowadays the majority of medical students are women.
The right to go to medical school is a pie. You can't share it out amongst everyone. Once you allow more women in, fewer men can go. That's why some men fought the ending of quotas tooth and nail, just like they fought allowing women into other professions or giving women equal pay.