Ah, that's the difference between us, it's age and generational expectation. I did not expect any help with childcare. If either mil or my Mum offered to have ds for a week in the holidays, then I would drive him up and leave him for the week, and then do another 7 hour round trip to get him at the end. I was grateful for the help, but I waited til it was offered; there was no expectation that it would be forthcoming. We budgeted for 48 weeks a year childcare and allowed for dh looking after him for two weeks, and then me having him for two weeks.
On a day to day basis, you sorted yourself out, and coped, especially as there was no alternative with geographical proximity.
I chose to have ds; it was my responsibility to look after him (and as he is in his last year of university, doing his MA, without any loans whatsoever, arguably, we have done that), but I didn't have him thinking he will have kids and I'll have to do childcare. He may not want kids; I wasn't sure I did until I was 29.
Given that women of my age (born mid 60s) now don't get their state pensions til they are 67, my friend and I could potentially be working well into our 60s, so that one won't wash I'm afraid. Have just calculated my friend's state pension age and hers is 67 as well. Should she be juggling working and childcare? I would also point out that our pension age may also move right. It already has by 7 years.
Wait til you hit your 50s, and you might want to revisit your opinions. At 40 I was working a 60 hour week as a secondary school teacher, doing all the domestics and school runs as dh was posted overseas. The thought of returning to teaching when we get back to the UK fills me with horror, as I couldn't cope with it now I've been able to get some distance from it. I'd be on my knees after a week. You do slow down; any aches and pains can get worse, and can be permanent.
I don't think my friend is mean spirited at all; but she knows her kids, and can see a situation where she is guilt tripped into doing far more child care than she wants to avoid sibling strife. Her dh is also of the attitude that they have provided for, and still do provide for the kids (in terms of financial help where needed), but at some stage they have to stand on their own two feet. If they feel mature enough to become parents themselves, then they have to take responsibility for their kids and not rely on their own parents to sort them out. If she helped out as you think she should do, she would have three under 5s (and maybe three dogs) for part of the week. That's a lot for someone to cope with, especially as it would be year round, given care would be needed in the holidays.