OP I totally get it.
My new born was in the back of an ambulance unable to breathe (we later found out she had severe asthma) and we didn't know if she would make it. I called my parents to collect my other child as she was terrified and we were dealing with the doctors and my baby, and my dad said 'no, mum had a cold'.....
I knew then, at that moment, the two people I should be able to count on in the world could never be relied on to help - not even in a dire emergency like that they were never going to step up. Not only that but the complete lack of care, love for their own baby grandchildren was really quite evident. I was quietly and silently furious - the type of anger difficult put into words. It burnt through me for months.
In fact it was one of many many examples of being totally let down by them.
I did the following shortly afterwards:
I sourced a very local babysitter/mothers help that I could rely on in an emergency and used her a lot as someone to babysit/look after dc so they knew and trusted her. I appreciate you might not have the funds for that, but it was cheap enough for a few hours a week, and she was lovely! And so good with the dc
We made a short list of friends that could be called and were there for us, and invested heavily into that friendship and we all helped each other
We knew never ever to ask them for help again, there was no point
I established a plan A, B and C for all eventualities.
I got to know my neighbours well (as it turns out we help them a lot, but I am happy to, they are great)
I stopped seeing my dp as much - went low contact - and spent more time with people that loved us properly
We became properly independent, managed all of our problems ourselves. We used all sorts of things, after school care, activities, baby sitters etc to manage - and we did.
Dc are now teens, they really are capable of caring for themselves now, and have zero relationship with gps. My mum always laments that she doesn't have a close bond with them, but she didn't earn it. She didn't put in the work, love and time with them when they were young, so they are hardly going to waste their young lives doting on indifferent grandparents.