OP, I totally understand ur heartache n frustration. Until one week ago, I believed that my father (whom I envisioned would have been banging down the door to see DD) n his partner (my mother passed away in 2000) have demonstrated 'polite interest' while I was pregnant, n since DD was born.
I lived with my father n his partner for a few yrs, and while I believe Partner is the polar opposite of my mother (those issues are a whole other kettle of fish), as an adult, I felt I had no true right to voice my feelings towards her - overall, Dad appeared happy, and was moving on. During that time, I remember her saying she'd done her parenting time, and didn't believe in being the permanent babysitter to her grand kids. Fine. But my family is very close, which included constant n emotionally intimate contact.
Fast forward 7 or so yrs. So, as I mentioned, I received what I called 'polite interest' from Dad n Partner. Which broke my heart. Dropping in on their way to Bunnings (20mins). One babysitting night (4?hrs), and the 'jokes' started before I even left the house about crying babies left to cry, n how many cigarettes they had brought to get thru the evening.
Anyhoo. Last week after a major family event, I was able to tell Dad how I felt, n he does want to be the involved GParent, however his partner truly is the indifferent one. So. Now we're working on it.
I disagree that 'our generation' just expects our parents are automatic babysitters. The culture in my family was that of all the generations looking after each other. Now, how it is in other families, I cannot answer, but I resent that statement.
Yes. Some parents are not cut of the same cloth as others - we can forget that each parent is ultimately an individual, with differing personalities, likes n dislikes, n their own expectations of their 'roles' as GParent. Even still, it still hurts when we realise that our parents may have a limited interest in our amazing little creations - their own flesh n blood.