English pronouns are a mess, and there’s no getting around the fact.
We’re missing a second-person plural in the standard dialect, which hinders translation into and out of languages that have it. All the possible alternatives – y’all, youse, yez, yinz and so forth – are strongly marked for region, or social class, or both, and using one of them would inject unintended meanings into the text.
We used to have some dual pronouns to go along with the singular and the plural – pronouns for “the two of you” and “the two of us” – but those were gone by the late Anglo-Saxon period. (We know English used to have them because they turn up in Beowulf, in the passage where Beowulf and Unferth are having their disagreement about what actually went down during Beowulf’s youthful swimming-match with his friend Breca – Unferth says “the-two-of-you did such-and-such” and Beowulf counters with “the-two-of-us did something-else.” One of the accidental uses of poetry is that it can act to preserve old words and old usages, fixing them in the amber of verse and scansion.)
These days, the lack that’s most keenly felt in the pronoun department is the need for a gender-neutral third-person pronoun. There’s less and less patience for the old-fashioned “everybody/he” (as in “Everybody took his tray into the dining room”), and not much more for the clunky if more accurate “everybody/he or she” (“Everybody took his or her tray into the dining room”), and the purists aren’t going to throw in the towel anytime soon on the issue of “everybody/they” (Everybody took their tray into the dining hall.”
There are a number of coined gender-neutral pronouns in circulation these days – ze, zhe, zie, and others – but no one set appears to be gaining an advantage over the rest. (Though they have given rise to a new etiquette rule for the twenty-first century: “Call people by the pronoun they prefer, not the one you think that they ought to prefer.”)
My money, though, is still on “they.” It has historical precedent in its favor, it’s in current colloquial use across a variety of regions and social classes, and using it doesn’t require a commitment on the speaker’s part to any particular social or political agenda.