Agree with this.
Family members make their own choices and those choices have effects on both sides.
Also, relationships are transactional to a certain extent, OP.
Few would want to tolerate constantly giving and getting very little in return or nothing at all even worse if giving and getting insulted or ignored.
Also OP, have you ever been a carer for an elderly person? I have and it is actually way more tiring than doing so for a baby/child, ime.
I was a carer for my grandmother and am a carer for my disabled son with two other children and being a carer for my grandmother even with my physically able parents was harder due to the dynamic and her needs.
The dynamic is harder because you’re dealing with an elderly person, not a child you have raised yourself and have built a structure with them from birth. Adults have their own opinions, they want things their own way and you cannot force them even if it’s for their own health, it’s harder to help them clean and wash compared to a child, they may need help to the loo or incontinent and you will have to change their pants. There’s some loss of dignity even if that person is family.
Would you be comfortable with your in-laws or an adult child you weren’t close to or comfortable with and vice versa seeing you nude, changing your pads and bedding because you soiled them? There’s also the likelihood of medications, timings, whether they can do it themselves, need to be watched while doing it, or you having to do it. What medications do they need? Are they daily, weekly? Injections, orally? Will there be suppositories involved due to side effects of other medications? Can they make their own meals or will you have to do it, is there a special diet they are on? Will they need people to come in and if so, who is paying for that? Add in years of doing this and the effects on the carer and the family. My mother was sad when her mum died but she was also very relieved not to have her life beholden to the caring responsibilities anymore.
I will not be doing any caring responsibilities or a lot of help for my mother and definitely not for my MIL. I will do what I can in my own capacity which is not much considering my own situation. My parents have said they will sort themselves after the caring responsibilities they did for my mother’s parents and not wanting it to be placed on my sister and I, even more so with us having our own children.
My MIL, it’s between her and my husband and knowing him he won’t either, again live hours away, 3 children, one disabled . MIL has plenty of other family members and friends including her daughter who is an actual medical professional. Her other son lives in Canada with his wife and children.