I think The Irishman is closer to historical drama than fiction, but given the subject matter, it's hard to imagine you'll ever get the whole truth from those involved.
One could maybe say that about the book it's based on... But Hollywood has a bad record of "based on a true story." And as you point out, the whole truth seems like it might admit to a lot of crimes that could be used to prosecute people.
You do not need to look at fiction. Look at almost any taxpayer funded pension plan. It will have tiers of benefits, where the older employees have better benefits than younger employees.
The older employees also happen to be the union leaders.