Do they still teach that?

Nobody talks like that and they(singular) has been common since the 1300s.

"But it's not proper English grammar!"

It's not? Shakespeare used it and last I heard that dude had a pretty good command of the English language.

"But it's not how it was used traditionally!"

So what? What is a human language if not fluid and constantly evolving? Language should reflect culture and social ideals, and our culture is rapidly shifting toward things like gender inclusively and social justice. When was the last time you used Æ or Þ?

And then in some languages, the word person is feminine, so you use she.

Not confusing at all