I think a modern USA 1 year old has about a 99.97% chance of making it to adulthood. That means that if a modern USA adult loses a young child, there's a decent chance they don't know anybody who has had that experience.

The ancient (and even, as you point out, very slightly pre-modern) world had a lot of "infrastructure" in place to deal with this, there were rituals and ceremonies and familiar people who knew what you were going through, and most of that is gone now.

It is indeed an enormous change.