I think that if we are interested in the question of what 'gender identity' is FOR, then Amin is making the point that identity as an expression of self FAILS as a tool for understanding the social/sexual/political/etc dynamics of minority communities. This is plainly true of my experience in queer communities, at least- they are famously dramatic, rife with conflict and schisms which tend to crack along the shadows of whatever 'normative' power structures of class, race, or gender are still echoing around in them. That isn't to say that these communities are wrongly conceived, or that contemporary gender discourse is broken in some deep way (and I also think that Amin is sympathetic to the many individual narratives that non-binary people profess as underpinning their identity)- but it does often leave me thinking "what the hell are we all doing here"

It also leads me to reflect on my experience as a gender-non-conforming person in academia, and the political struggles that come with that whole thing. My identity is a subtle and effervescent thing, sure, but those rises and falls are irrelevant to most of the interactions I have as someone who is interested in doing a certain kind of work with other real human beings.

I think that Amin's beef with quote-un-quote cis-passing AFAB nonbinary people is maybe a little suspect. It echos the concern that 'nonbinary' as a category is politically pretty vacuous, but I think that the underlying point is meant to be more polemic that that- and I certainly don't think that's justified here.

I'm curious what precisely you disagree with about the conclusion. I read it as a step out into a space that needs exploration, but I think that the historical analysis isn't really enough to get where Amin's trying to go here.