OP. I think the answer to your question "Am I gender critical" is yes, you have articulated the beliefs of most GC people, you too are now firmly in the transphobic camp, causing literal violence to thousands of innocent transgendered souls. To test it out, try discussing this with anybody on twitter with pronouns in their bio. Actually don't, I've done it and it's terrifying , they are entrenched and it's much scarier than mumsnet.
It's strange because you are talking about non aggressive strategies, that to me seem to be exactly what is being done anyway, but now also talking about fighting ideology with ideology and battles and wars.
Your definition of transgender was-" Someone who does not believe they conform to gender norms, as they perceive them and starts to express/present themselves according to how they feel."
I think that is a better description of a gender non conforming person or a non-binary identity. It may also cover sensible old school transexuals, attempting to relieve dysphoria, but it is not how MtF or FtM transgender people, who believe in gender identity and gendered souls and being born in the wrong body see themselves. TWAW and TMAM remember and all the allies believe this too. #NODEBATE #NoCompromise. Any deviation from this will incur cultural wrath.
But whether non- binary or trans, gender ideology takes the abstract concept of gender and reifies it (makes it concrete), in order for selected chosen people to be able to escape it or step outside of it altogether.
It then takes the concrete reality of biological sex and tries to make it into an abstract concept of lesser significance.
Having solidified a pink and blue box (which trans individuals can then move between) or reject altogether, it creates the box/label "cis" for everyone else.
They cannot think about gender in any other way, or there would cease to be a means by which they are oppressed and nothing to escape from or to, they need gender and they need it to be rigid for most people, as indeed it it is for them in the abstract. Without it, they can't disidentify from it and there is no ideology or opressive societal structure.
This is about people who believe in boxes, but at the same time believe they are feeing the world from boxes.
You are on a forum of people who genuinely don't believe in gender boxes, but regretably acknowledge the need to distinguish between people based on sex, because they get put in a box because of their sex.
Your arguement about approaching it side on (I think)is that the content of the boxes should be debated as a way of compromise (as in, both boxes should be acknowledged but understood to contain the same things). This is largely what we do, or rather the line is " do what you want with the boxes, but these are the modest boundaries we need you to respect". If both gender boxes contain the same, there are no boxes, so GC folk are happy...but biological sex still exists and needs acknowledging.
Members of the public who feel strongly that there are gender boxes, may be persuadable, so there may be some value to your approach here, but then they would become gender critical...and biological sex still exists and needs acknowledging.
The trans ideologues will still not be happy. They need those boxes, more than anyone, for round them their world view rotates. They don't see it as a stepping stone, or they would be able to acknowledge and understand gender non conformity. They utterly reject the concept of sex based rights and in the mean time...biological sex still exists and needs acknowledging.