That's typically an economic issue, not a personhood issue. Not that it's a bad thing to share housing between generations, it should be normalized as it was not long ago.
For us we have three generations under one roof because it works. Everyone pitches in, and having a grandparent around for occasional childcare is a godsend. Eventually we will be the carers as they get into advanced age. There was a period of learning to let go of individual cultural hangups, but we all got over it in our own time.
The idea of every couple having their own individual single-family home, kicking kids out the moment they turn 18, and letting grandma either fend for herself or go into a nursing home (which will swallow any inheritance that exists) is not just cruel, it's completely unsustainable.