Why should we stop with gender fluidity?

Worried that the surprise I felt that "detransitioning, the process of reverting to the sex assigned at birth" and its accompanying moral dilemmas had been deemed worthy of an NPR segment (as if public funds could not be better spent on subjects that are, shall we say, less niche) means I am small-minded, I decided to try to think big.  Really big.

I admit that in our age of gender fluidity, when, as I understand it, ex-men bear the children of ex-women, it is not easy to imagine further progress.  Yet here are my thoughts, for what they are worth.  

For one, what is a human but a creature that, when under its own power, just crawls on the dry land?  Birds fly in the air.  Fish move comfortably under the water.  So why not grow fins and wings?  Modern air travel is costly; besides, flying under one's own power is better for the environment and would be, without doubt, good exercise.  Same with sea travel.  So why not, in addition to being gender-fluid, become species-fluid?

Time is a challenging frontier, too.  It carries us with its flow.  We are born at a fixed point in the past, and the present inexorably increases our age.  But how about becoming birth date fluid?  If we can be of any gender we want, how about being of any age we want?  It would be very convenient.  Why go through growing, study, and work?  As soon as one can speak, one can declare oneself of a retirement age, and right away start collecting Social Security.  The ability to dial one's age back may also come in handy.  What if one feels like engaging in activity defined by law as statutory rape?  Birth date fluidity would allow one to avoid jail by telling the judge that prior to the act, one's birth date got fluided to the age of the victim.  The benefits of gender fluidity that merely allow one to use the opposite sex's bathroom, or to compete against the opposite sex in sports, do not even begin to compare.  Being species fluid, or birth date fluid, is really the thing.

Well, that NPR segment really did get me going.  Yet who knows?  Perhaps, years back, the talk of "gender-fluidity" was considered nuts, too — and now it is, in all earnestness, it seems, being discussed on public radio, on the public dime.  So maybe, in a few decades, we will indeed fly like birds, swim like fishes, and collect Social Security from birth.  After all, gender-fluid ex-men do give birth.

Or do they...?