The puns here have endeared this card to me.

I think you mean "their" or "his or her"?

e, er, em are short, efficient, universal third-person pronouns for any gender or plurality.

They're not universal unless they're in common usage, which they aren't. It would be nice for a nongendered pronoun for the singular third person to come into use, though.

e/er/em are efficient within the rather small communities where they're understood. The usage hasn't spread anywhere near widely enough outside of Tumblr to be comprehensible on a general-audience product, for the moment. they/their/them is the best option for a nongendered singual 3p pronoun in general use at the moment.

universal = general, adaptable to many functions or uses. didn't mean ubiquitous.

nevertheless, similar forms are widespread if you look outside english and european languages at languages with light or no distinction of gender (in pronouns). so really the reason this can't be universal for english speakers seems to be er narrow worldview and er stubbornness to accept that gendered pronouns are not universal or obligatory.

they/their/them certainly has some clout and tenure from usage in hundreds of years of english literature. but logically doesn't fit in many situations, resulting in counter-intuitiveness. thus the refusal from rational minds to accept them as the ultimate pronoun.

my goal is not to appease gender politics. my modus operandi is simplicity, rationality, efficiency. the trend to seek "better" pronouns is merely an opportunity to challenge my creative urges.