To identify outside the binary is not to be undecided but to decline a choice that does not describe your actual experience — to say that the categories on offer are insufficient rather than that you are. Non-binary identities ask everyone to examine what they assume about gender and why those assumptions feel so stable and so obvious; the resistance such identities provoke is often evidence of how much work the binary is doing to hold a particular social order together. The question is not what to do with people who don't fit, but what the ill-fit reveals about the container.
Each step builds on the last.