Definitely not all boomers, as my parents have never allowed my babies to cry, my MIL wouldn't do that either. It's horrible, so damaging to babies!
My baba was a classic boomer stereotype and this was one of the things she used to say often. She also made comments about my cousin always holding / wearing her baby. She would slyly ask me if my mother grew up insecure or craving attachment because of the way she was raised. Finally one day I said to her "If she did, she certainly wouldn't say so" and my mom, who happened to be present, agreed. Never heard a word about it after that. Lol.
Got told several times by my own mum to CIO when my LO was a newborn. Politely told her, that isn't something I wanted to do. The more she pressed, the more details I gave about how it's bad for the baby and research shows it damage the babies emotional development. She eventually stopped telling me to do it 🤷♀️but that could also be the fact she told me it didn't do me any harm and I responded very sarcastically, yea, coz I'm emotionally well adjusted 🤣 but still, it's your baby, you choose methods and she needs to shut her pie hole :)