My parents do this with my nephew. He has changed his name and they still call him by his female birth name. I’ve tried to tell them, if you don’t understand it, fine, but respect it and deal with it. But old people are just too stubborn.
When he came out as trans, the rest of us were like “yeah we figured, congrats!” It was no surprise to anyone who saw him growing up except my parents
My aunts and uncles are well into their 70s and 80s and have by far been the most supportive people in my life after coming out. Being an asshole has nothing to do with age.