That's what gender-scepticism is or being gender-critical. The position that gender is entirely a cultural construct and one which was constructed to oppress women. It must be done away with. Accordingly, trans identity makes no sense because there is no innate gender. 1/2
People can be sceptical of trans identity for all sorts of reasons that are not gender-skepticism though, obviously. Many people believe gender differences exist AND that trans identity is a delusion. These people are not gender-skeptical feminists tho. Different rationale.