My alcoholic father has been in counselling. It started out as court-ordered but he willingly kept going for some time afterwards. I don't know if he still goes as the counselling was a free service so he'd probably have to pay to go private once he'd used up whatever was allocated to him (and both my parents growing up were very dismissive of mental health), but that short stint did have some impact - he sent one text where he said he'd realised he'd had a violent childhood which had caused him to be neglectful.

It was nice but nowhere near enough. I also don't feel any void in my life from where my parents were supposed to be. I don't miss them, so it doesn't feel worth it to force a relationship with them even if they're going to therapy and want one.