Also, “Mary Sue” is not a dogwhistle. There are plenty of well known male Mary Sues/Gary Stus in fiction. I’m not sure what you’re implying about Marcia Lucas with that. I know people who avoid using the term because they don’t want to be accused of being some sort of reactionary, but it’s a valid term in character criticism.
I agree that it’s valid, but it’s been used so often by the reactionary sort that it has kind of lost a lot of its original meaning and has become a dogwhistle for some (akin to “ethics in video game journalism”). It sucks that such a useful term has been ruined, but that’s the impact of the culture war on pop culture discussion.