Dude, Shakespeare is basically the epitome of English writing.

If your argument is that it’s new, well you’re fucking wrong because one of the most renowned writers of English used it centuries ago, as well as some translations of the Bible and other things.

If your argument is that grammar changes well then I’m sorry you’re several centuries behind on this development. This one isn’t new, however much of how we speak and write today is significantly newer. Notice no “thou art” or anything like that in either of our comments.

https://www.englishgratis.com/1/wikibooks/english/singularthey.htm

There’s not a man I meet but doth salute me / As if I were their well-acquainted friend — Shakespeare, The Comedy of Errors, Act IV, Scene 3, 1594

'Tis meet that some more audience than a mother, since nature makes them partial, should o’erhear the speech. — Shakespeare, Hamlet, Act III, Scene 3, 1600–1602

So lyke wyse shall my hevenly father do vnto you except ye forgeve with youre hertes eache one to his brother their treaspases. — Tyndale’s Bible, 1526

All of these are centuries old, and each of them know the gender of whom they speak of. You are incorrect. Please update your knowledge and don’t correct someone for something you didn’t at least look up.