On a more serious note, I think a good measure to use is agency over the self. A character that is helpless but otherwise is the master of her own person does women more service than a "powerful" character who is entirely defined by being on strings yanked about by others.

Characters primarily defined by their relation to other characters are narratively weak.

I think it's more of a jealousy/lowering of standards kind of thing. With a lot of the crazy feminists usually being psychotic, ugly cunts or just lathering themselves in makeup, they tend to get upset that other women are seen as attractive and not them. Sort of how you might sometimes see people that are fit and work out get harassed because their existence alone is considered fat shaming.

Obviously you can't harass actresses over their looks, it'd make their side look bad. So they just bitch about any moderately attractive fictional female character that people like. Or when they get their hands on an IP they make sure the creators make them look as ugly or androgynous as possible.