Fun fact: there has been more time between the first use of singular they and today than there was between the first use of plural they and the start of the criticism of singular they
I was gonna say... The use of singular they has been around for a heck of a lot longer than 11 years. I didn't realize it dated all the way back to the 14th century though, that's neat.
I get the point, that it wasn't in common use until somewhat recently (even growing up I had textbooks that used he exclusively), but it's not a new radical concept of the English language either.