Although of course that a) could well hide some uncomfortable biases
For sure. But, pragmatically speaking, you have to play the game to win. I think the Democrats would take winning with an imperfect candidate over taking a principled stand against latent discrimination and potentially seeing Trump win a second term.
Also, if we're both hinting subtly at a bias against women (and I think we are), that may not be the case either. I reckon if AOC was old enough to be eligible, she'd be a shoe-in.