Letting Go is the Loving Thing
You can love someone that needs brain surgery, but love won't help them. They need brain surgeon. You can love a parent, but not be the best person to care for them anymore. It really is that simple. People are living longer, and often with more serious or debilitating conditions. Loving our parent doesn't mean we are the best people to care for them, 24/7, for the last 25 years of their life, no matter how bad they get.
You are a good person for caring and wanting to help your parents, but the reason caregivers become so angry and upset now is because they've gone way beyond what they can or should do.
Parents have to want to help themselves and be able to help themselves. If they can't and/or don't wish to, they need to be in care. we need to allow our parent to go into a facility where they will get care.
Medicare and/or Medicaid pays for care if they don't have the money. Some states have programs that will send out people to care for the elderly, in their own apartments, etc.
You are not required by law to take in your parent, or to keep your parent once they do move in. You are not required to pay for your parent if your parent doesn't have the money to pay for care or a nursing home. Never sign anything that obligates you to pay for their care or housing.
Your parent may be filled with anger and bitterness or have dementia or physical issues, but those are not things you can fix. Accept they feel that way or are that way, but you are not to blame and nothing you do can fix it.
Accept the reality of the situation, you are not qualified to provide the care they need. Make peace with yourself that doing the right and loving thing for them by letting them go into care.