The theory of performativity does not assert that gender is “a performance” but rather that gender is performed—a subtle but very important distinction that Judith Butler—the theorist who developed the theory of gender performativity—has gone through great lengths to try to explain because of how often this theory is misunderstood. To say gender is performative means it is based in repeated imitations of cultural norms whose substance depends on their repetition. It’s a way of examining how gender is “done” in the material world, not a way to reduce gender to an immaterial gesture. Butler’s second book (Bodies That Matter) is a response to how systematically gender performativity was (mis)understood and disconnected from materiality. In fact, one could argue that performativity and materiality are intimately connected because the materiality of gender (the real life consequences that result from transgressing gender norms) is based more broadly in the repeated enactment of gender norms, not some essential characteristic that is proposed to underlie all genders. I actually wrote an essay on Medium about this a few years ago called “(Mis)Understanding Gender Performativity” that addresses this common misinterpretation of Butler’s theory. I mean you no disrespect in disagreeing with your position, though; I’m trans as well and study performance theory so I thought I would chime in because performativity actually helped me clarify the social nature of gender dysphoria and leverage against the essentialist pathologization western psychology forces us into by saying our dysphoria is based in a discrepancy between our genitals and gender identity instead of the distress from the ritualized punishments we face for transgressing gender norms.