The baby is crying because they want attachment to the parent. Give them the love they want. Don't deprive them of love by letting them cry it out. Comfort them!
You're not wrong. But at the same time... it's a very effective method with some babies. One thing often missing from these discussions is the practicality. Yes, responding to your child like that would be ideal. But it just can't be done if they literally just cry constantly when put to bed. And some babies do that! Sleep-deprived parents who come to actively resent their child's crying is a very real thing. And probably far worse for development and attachment.