A boomer is someone, usually older but not necessarily an actual baby boomer, that is insufferably obtuse and close minded. Usually displays curmudgeonly behavior
The back in my day mentality is something a lot of boomers parrot, as well as the word entitlement because if the new guys aren't getting bent over like you did back in the day then they're entitled
"The children now love luxury; they have bad manners, contempt for authority; they show disrespect for elders and love chatter in place of exercise. Children are now tyrants, not the servants of their households. They no longer rise when elders enter the room. They contradict their parents, chatter before company, gobble up dainties at the table, cross their legs, and tyrannize their teachers."
Socrates
Basically the boomer mentality has been going on for thousands of years. Even I have begun to display boomer like tendencies towards people 10+ years younger than me, but then I catch myself because I know what it's like to be in their shoes and have to listen to that nonsense
Every generation talks shit about the ones that come after it. The silent generation talked shit about the boomers and the counterculture movement, boomers talk shit about millennials, some millennials talk shit about gen z. It's definitely fun sometimes but I wouldn't let it go beyond a joke, otherwise you're being a boomer