Well, I don't think everyone's situation is as extreme as mine, so I don't expect that others would have these boundaries...
I've been no contact with my mom for about 12 years now. 12 blissful years, I might add. She knows that if she is willing to do therapy with me, that's where I will see her, in a therapist's office, where there is an actual witness. She has some profound and untreated mental health disorders and will flat out lie, all sorts of crazymaking behavior and is very emotionally dangerous. (She was physically dangerous to us until we became adults.)
In my case, I do write her off forever. With her borderline personality disorder and what's properly termed as "personality disorder with tendencies toward narcissism", she is very highly unlikely to get help. To even admit she needs help. It's very, very sad. My sister and I have chosen to protect our families... mom has done some very bad, bad things to my niece and nephews. It's unfortunate to cut her off, but that's what good parents have to do sometimes. I have low expectations at this point. At first, honestly, it just killed me to do this. It killed me that she didn't love me enough to want to try to make things better. I have cried and mourned this as a death, and for the most part, it's like she's dead. Staying hopeful is not healthy, helpful or realistic; acceptance has been a hard gift, but it's better than living the rest of my life hoping for something that isn't going to happen. I think we all know of situations like that-- it makes people stop living, it makes them bitter. Choosing to move on means living fully in my situation. I'm not sure what yours is, but I know it's a hard place to be in.
For what it's worth, there are boards online like BPDfamily (google it) which can offer support if you are dealing with borderline personality disorder or narcissistic behavior. I suggest this because sometimes, these are unique situations which people who haven't experienced may not understand or may be judgmental of. (I've found in my own life that most people can't relate to our understand my past because they had half-way healthy parents. They can't fathom people acting like my parent did.) Finding people who have 'been there' to advise you could be very helpful. Many people go low-contact successfully with family members who exhibit these sorts of mental illness, so it is possible. Good luck!
ETA: I would be remiss if I didn't add this-- we do have some of the problems you listed with some of the family we are in contact with. We've made very good, strong boundaries with the really problematic behaviors, and also limit the amount of time we spend with them. In short, we actively manage those relationships as necessary.