The classical "gender critical" position — really the Trans Exclusive Radical Feminist position, as "gender critical" is a fairly recent term — is that there is something innate to cis women that cannot be present in anyone not born with XX chromosomes. They talk around the issue a lot by, among other things, inventing a sort of "innate violence" that all men have and thus, in their eyes, all trans women have, and thus they think we are a danger to cis women, but really, the classical TERF position is an almost religious reverence for the concept of a "female soul". Classic TERFs have a whole academic structure they've built around this shining pearl of shit but always, if you keep questioning them, it comes down to, "I've got something inside me you haven't got and never will."
Modern TERFs and gender critical people don't come from this tradition. Modern "gender crits" are naked bigotry with no attempt to justify it. They're the Q Anon of gender, they hang out in forums and Discords and on the arse-end of Twitter and Reddit and share their basest fears trumped up into "facts": trans women will replace "real" women; trans men are erasing "real" women; trans people are trying to convert/steal our children. If you switch the words around you can see it's just recycled homophobia, racism and antisemitism, which isn't a coincidence as these people are mostly also homophobic, racist and antisemitic.
Classical TERFs and modern gender crits do work together, and it's often difficult to tell the two groups apart — particularly in, say, the modern UK media — but they also fight a lot, and one of the things they are currently disagreeing on is whether or not they should ally with the extreme right wing in order to achieve their trans-exterminationist goals: classical TERFs mostly say no, because they are still hung up on their goal of protecting women (potentially admirable, but they have entirely the wrong target) and rightly see the right-wing as disastrous for abortion, women's rights, lesbians' rights, etc.; modern gender crits are mostly all for allying with Trump, Boris Johnson, the current Polish government which has targeted LGBTQ people and abortion, and other people and groups on the extreme right, because they have the Q/white supremacist worldview that states nothing is more important than their chosen existential terror (the elimination of "woman" as a concept / the elimination of "white" as a concept).
So it's why it doesn't make sense: trying to analyse it seriously is like punching air, because there's nothing there. In both cases it's a cloud of excuses around a central fear or bigotry.