As parents we only need to aim for "good enough" - because perfect is impossible - and the bond of attachment is so strong it easily overrides small imperfections.
And while that separation is natural, necessary even, if the relationship is too disappointing, or even worse clearly abusive, then paradoxically that process of moving away can be harder.
Why? Well, it's natural to seek out comfort, and what we need emotionally, from our parents. And if our childhood environment leads to more distress, we are hardwired to turn to our primary attachment figures - even if it doesn't always help.
Nonetheless, we keep trying. Attachment glues us together and can keep us locked in a cycle of hope, disappointment and hurt.
It sounds like this is where you are, and it's not uncommon for people to turn to therapy to figure this out.
And while it's natural to keep trying to change them - to feel you have to work on the relationship by telling them about how you need them to be different - the way out of where you're at is acceptance, along with making space for grief.
Grief not just for what you didn't get as a child, and can't get now, but grief for the parent that you never had. You know, the perfect one, or even just the good enough one.
The one that didn't disappoint you, didn't misunderstand you. Just got you.
Because holding out and wishing for that parent to show up is completely natural. But only when we can truly accept what is, and grieve for what will never be, can we free ourselves up to actually respond effectively to the present day relationship and the person our parent is now.
To figure out how, or even if we can, have an effective, adult to adult relationship with them.
I hope you can. Often when we truly get to a place of acceptance and can let go of change as the solution, it gets easier.
Then we get to see that our parents are just flawed imperfect human beings like the rest of us - doing the best with what they have.
For some, sadly, this kind of resolution isn't possible, and cutting off contact is ultimately necessary. But it doesn't sound like you're there yet.
Your mother might not be the best emotional support. But perhaps there are other aspects of the relationship you can focus on, with acceptance it becomes possible to play to the strengths of the relationship. And lean on others - who do have that skill - for the emotional support you need.