"Singular they" does have a long history in English, and cannot be considered wrong. It has been more favored in recent decades to avoid "default he", that is, the use of male pronouns for a person of unknown or unspecified gender. That has a much longer history in English than "Singular they" does, but is now considered to show gender bias and is strongly frowned on by many people. It does avoid writing "s/he" or "he/she" or "he or she". On the other hand, it loses the information about singular vs plural.
Personally, I strongly dislike singular they and will not write it under any circumstances whatsoever. I will usually use "s/he" or "he or she", which I do not find at all awkward. I do not know any people who have expressed specific pronoun preferences to me – I am not sure how I would handle the case if I had occasion to write of a person who preferred to use "they". I might add that if personal preferences are allowed in such matters, that I prefer not to be referred to as "they", except as part of a group.
At one time I hoped for consensus to form on a new, coined pronoun for a singular person of unspecified case. I favored "zie" with objective case "zir" and possessive "zis". But no wide consensus on this has developed, and I do not now expect one in my lifetime.