I’m old. Back in my day (do I sound like your grandfather yet) we did our best to be inclusive by using he/she and him/her or, if we were cool, s/he. Using “they” to convey a singular pronoun was considered poor grammar. We looked down our noses at folks who said, “If a person wants a banana, they just have to ask for it.” Nopety. Nope. Nope. Nope.
Times have changed.
Dennis Baron, Professor of English and linguistics at University of Illinois explains in his blog article A Brief History of Singular ‘they’ declares, “Singular they has become the pronoun of choice to replace he and she . . . .” He also explains how that came to be.
It still stops me cold when I see it in print, but I’m trying to adapt. What say you?