Yes all marines are riflemen. That doesn’t mean that you have to deploy women in infantry units.
But their overall tactical performance in the field was noticeably worse, and they could not keep up on conditioning hikes. And that's when compared to the average male Marine, not to grunts.
The Commandant was absolutely right on keeping women out of those MOS's. Too bad most of our politicians lacked the cojones to back him up.