I didn't say it was simple. But it's perfectly possible, there is no legal obstacle to it and - unlike race - is a matter over which you have choice. If you decide not to make that choice, that's fine. But you must accept that there may be negative consequences to that decision.
Besides, it's not this society's job to make it simple. It's the job of the individual to adapt to society, not the other way around. Thinking it is society's job to adapt is what has dropped us in the sh1t.