The best thing you can do is realize these are unique individuals. They’re your parents, sure, but it’s not your responsibility. Live your life, let them live theirs. It’s ridiculous the way we as a society have normalized the idea that we need to care for our parents.
Don't blame the kids for "normalizing" what their parents did. I couldn't have changed the choices my mother made, obviously not when I was still an infant but really even much later. As you say, parents are unique individuals living their own lives. If their choices eventually lead to them being unable to look after themselves, what are the children to do? Let them starve or freeze to death on the street?
Like it or not, we all do have a responsibility to look after those who can't look after themselves, even if they're not related but even more so if they spent years of their own lives looking after us. There seem to be people here who would prioritize getting the latest greatest 4K OLED monitor over ensuring their own parents' welfare, and that's literally monstrous (look it up).
Spending years of your life rearing a child is your decision and obligation as a parent. It’s not fair to put that on children to care for their parents, particularly when they’re stubborn and when childhood trauma is involved. We didn’t all grow up in good environments.
No, we didn't, and you should be more careful making convenient assumptions about your interlocutors. If you want to make exceptions because of extreme circumstances that's fine, but that's a far cry from your original "unique individuals" argument. Almost seems evasive TBH. The normal case is that people deserve to live with basic human dignity even if they might have made some poor choices. Does that create a burden for others sometimes? Yup, sure does. It's this little thing we call civilization. And where there's a burden there's always a question of who should bear it. Again, the normal case is that it would be those who are already reaping what their parents helped them sow. This is not some super exotic or recent philosophical idea. If anything, the idea that you don't owe anyone else anything at all no matter what they've done for you or how that plays out when everyone's acting that way is the newcomer, still wanting for evidence that it can lead to anything good. Most often, it's just rationalization for doing what's convenient instead of what's right.