Valid points, but at the same time—i get where Hyesung's mom came from. She was probably too ashamed to meet Hyesung on many ways. It's not like she was asking for money either, but i get your point.
But in many cases, she is growing old. You can't really get an easy job on a certain age level of age because most employers doubt your eligibility to work without health issues- despite your capacity to work either way.
Nevertheless, if we put it this way you could see why Dojin reached out to help. He still hoped that one day they be able to sit down and face each other when the wounds aren't hurting anymore.
In this way i feel like Hyesung too has finally came to terms that his Mother too had reasons, as to he also had his reason why he turned his back to Dojin and byul as well, and how it hurt Byul when he was told that his mother too did abandoned him at a certain point. It all comes to a certain piece of understanding, taking accountability properly close the wound for good.
Totally get your words, just wouldn’t necessarily compare Hyesung’s “abandoning” Byul (if I’m correct he was literally baby trapped and raped, inevitably pregnant, Dojin paid him to have the baby but he never took the money) with the granny abandoning him for nearly his whole life. It just feels incomparable to me because they were at different life stages and other things. But I get what you mean by the “they all have reasons” part.
I just think she could’ve brought him somewhere safer before leaving. Hyesung knew the baby was in the care of Dojin, he didn’t leave him in the hands of an abuser, nor start a new family. Hyesung was also kind of being led on to think this is fine by Dojin’s friend.
I don’t think there’s any accountability to be held, even with the granny as she is getting old. It’s not worth the drama. I’m hoping they talk, get closure, and move on. For the sake of peace.

I thought before like she was a victim too. So it's normal for her to escape and if it's true that she tried several times before to meet with Hye-sung but her ex-husband blocked.
Butttt
Then I thought why didn't she tried to meet with Hyesung when he was working as a waiter or when he was a highschooler. There could be no way her ex-husband would know. And she came up when Hyesung find himself a rich husband.???? When they meet she hurted Hyesung with her accusatory words. Even after all that (Hyesung never wanted to see or be near to her any more) Dojin bought her a house and send her montly money. WTF???? And I'll remind you after a house and allowence, she didn't tried to find a job. She just lived her luxury life like that. That annoys me