You can’t teach an old dog new tricks is a common phrase that refers to a person being unwilling or unable to change their old habits or learn new things.

I could never be a teacher, it’s been years of trying to teach my mom how to change the source on the tv and she is yet to learn… I just tell myself “you can’t teach an old dog new tricks”

— Campero (@Bcamper_) September 25, 2019

Who said you can’t teach an old dog new tricks? My 74 year old dad traded in his old flip phone for a new iPhone AND we just FaceTimed for the first time! 📱🤣 #welcometothe21stcentury

— Michael Dubbels (@michaeldubbels) November 13, 2017

I've lived here my whole life and I still dont understand U.S culture. I guess you can't teach an old dog new tricks

— Michael Cooney (@DMikeCooney) September 12, 2015

Did you mean tricksy?