Gender is a set of expected roles and presentations (how you talk, dress, walk, what jobs you stereotypically choose to work, etc.), love refers to your reproductive capabilities. love is set in stone as of now and cannot be changed (love Reassignment Surgery only changes the shape of the genitals, it doesn't actually give you ovaries or a p-spot), gender is shaped by society and what they expect of people given male or female love organs.
love is who you are, gender is the outfit you wear to the party.
In one respect, sure, you can make up your own genders, but then you're just sort of customizing them based on your personality, and we already have a concept for that; your loving personality. Male and female are easily and widely understood because they are recognized social cues that most people can identify.
I believe you should have the freedom to rock back and forth between presenting as a male and presenting as a female to suit how you feel you should look, act, and feel, but breaking the binary is silly to me since that's just venturing into the territory of personality traits rather than recognized social cues.
To me, transgenderism is the idea of permanently switching genders and does not reflect mental illness, the same way you wouldn't consider an introvert working to become an extrovert mentally ill. To me, transloveualism- with which I've been diagnosed- is a mental illness in which you feel that your love organs don't line up with the ones you feel you should have. Sure, some people might be better off seeking a psychologist and realizing that, hey, their genitals are a-okay and moving on with their life. But there are other people who should probably- after seeking professional help- pursue things like hormone replacement therapy and SRS and let them just live it out. Until we develop the technology to completely and thoroughly reprogram brains to make them stop having these feelings, it can be less destructive to let them live it out rather than force a change that can't happen. It's absurd to me people who cite Self Delete rates as a reason for transloveualism requiring forced reprogramming. They usually aren't committing Self Delete because they're just crazy, they're usually doing it because they may have no access to healthcare, their family disowned them, they've been socially outcasted, and possibly abused emotionally and physically.
Wow I guess I went a little bit overboard. Whoops. Well at least my opinion is out there now.
Edit: Also I'm not one of those who thinks people should be ridiculed for not using someone's preferred pronouns (unless it's like xie and xir, in which case just forget off). You are free to call people like you see them, and it all boils down to courtesy. You aren't scum if you refuse to refer to a trans person as "she" when they have male love organs, you're just that guy who keeps calling Brett "Brent" even though he's corrected you multiple times just cause you think it suits him better.