I don't think retired grandparents have any financial responsibility to their adult children or grandchildren. They should enjoy their own retirement, and where they have loads of money, travel the world, choose their own care home, access better medical treatment, etc. Enjoy the last of their years before their health deteriorates.
If any of their children or grandchildren are disabled, that might be different, but if the adult children are healthy and capable of working, it's down to them to support their own children themselves. However, to be really clear, I also think that the Government has a responsibility to ensure that two adults working full-time with, say, one or two children can actually afford to be independent.
If, say, a working couple is forced to use a food bank, something has gone seriously wrong, and the Government needs to intervene. I don't care whether that means raising salaries, cutting taxes for middle earners, increasing taxes for higher earners or creating top-up benefits for those in work - it's their problem to fix. You can't rely on intergenerational wealth to sort it because the problem is bigger than one family, and not everyone has a wealthy relative to fund them.
A working couple should be able to afford a simple (but not miserable) lifestyle for themselves and their kids without needing family to sub them.
PS It's a shame this Government is a shit show, and the reality is that plenty of working couples are struggling more than is reasonable.