Having been parentified by your mother, you understandably have resentment towards her. It sounds like she's never acknowledged the damage she did or apologized for her behavior. If it's pointless to discuss the matter with her, then you're left with a superficial relationship based on obligation and not much else.
I'm not sure why you feel guilty. Guilt is a response to having done something wrong so it belongs to your mother, not you. Feeling guilty for the situation could indicate that you're still stuck in that role reversal pattern of parentification. You're still being the grownup one in the relationship, responsible for connecting with your mom and caring about her emotions.
Most likely, you're not experiencing guilt but a deep and profound sadness for not having the kind of mother you wanted. When with your mom, you may feel angry about the way she treated you while growing up, robbing you of a carefree child. For these reasons, it's unpleasant to be with her. Limiting your time with her makes good sense. You need to have a healthy balance in your life and happy reciprocal relationships with other people.
With my mother, I've developed a routine whereby I check in with her but don't get sucked up in all her drama. I call once a week, talk about 15 minutes, and then say I need to go. I listen to what she has to say but no longer take on that parent role, giving advice and worrying about her. I no longer get overwhelmed with anxiety, listening to all her problems like I did as a kid.