Unpopular opinion coming up:
I don't like the term. I've been a feminist since about 1972 (from my early teens) when I read the Female Eunuch and Against Our Will.
I think "GC" is a term which describes a lot of women who haven't been involved in the women's liberation movement until the threat of transactivism hit them in the face (so maybe 6-8 years ago), and who tend to be focused on this one issue.
I hear a lot of women talking about the issue in a way that suggests they weren't really that bothered about feminism before. They assumed that we'd got all the rights we needed, that we're "equal" now. They can't help it, they were brought up in a sort of post-Thatcher liberal feminism.
I agree that transactivism is a huge problem - it is trying to undermine the foundational meaning of what it is to be a woman, but there's a lot more to feminism that being "gender critical" and I doubt a lot of women who say they are GC have thought much about what systems of gender actually mean.
But I've spent over 50 years working in and with feminist theory and activism, so I suppose I do dsort of look at very new "GC" feminists as a bit wet behind the ears, and think they need to do some reading about the long and very awesome history of feminism.
Starting with Mary Wollstonecraft maybe.