I see.
So you see the differences between 'the transes' and transgender people.
But you also don't acknowledge that a group of people will adopt dehumanising terms, that they have been vilified as, as a form of rebellion, which would account for some people using it as a badge of honour.
Very few people who are feminists drop the 'feminist' if they even use the 'gender critical' about themselves. They may however use the term to describe their beliefs such as 'gender critical beliefs'. eg. they may say they are 'gender critical', which is short for 'gender critical beliefs.'
It seems you don't understand the origins of the term 'gender critical' at all. But still, you wish to use the term 'the GC' as what, a form of retribution?
And the humanising suffix of 'ist' is why 'genderist' is already a humanised form of descriptor.
Gender ideologist or genderist would be the same as calling someone a feminism as someone up thread has already explained.
As I said, people can describe themselves as being 'gender critical' but this is again not comparative to being described as 'the GC'. In this form 'gender critical' is a description of a set of beliefs, but 'the GC' is describing a group of people.