Examples of the singular “they” being used to describe someone features as early as 1386 in Geoffrey Chaucer’s The Canterbury Tales and also in famous literary works like Shakespeare’s Hamlet in 1599.

“They” and “them” were still being used by literary authors to describe people in the 17th Century too - including by Jane Austin[sic] in her 1813 novel Pride and Prejudice.

https://www.bbc.com/news/newsbeat-49754930

Personally, I think I’ll keep using a pronoun the way that worked for Chaucer, Shakespeare and Austen.