In the end, the show is about family relationships, with a focus on broken families and the possible ways to achieve healing.
The world is not perfect. Parents argue, fight, get separated, and sadly get divorced; or a parent abandons their child. Whatever the reasons were of the adults, the most that is affected are their children. The world that turns into darkness are the world of the people adults brought into this harsh reality.
Suji and Uri showed us that this shouldn't be the case, and that we can achieve healing in one way or another. We may hate someone for what they did, but we shouldn't let that turn into bitterness. Suji and Uri taught us that forgiveness is a path that all of us can take, because the people who benefits the most from having a forgiving heart is no other than the person who learned to forgive. And that's where healing begins and we start seeing the light.
Which then leads to having a heart of gold to take care of other people going through hardships in life, like we did, and potentially adopt children who deserves to have beautiful world.
Yes, adopting will not change the world, but it will indeed change the person's world. You see, we were not born to change the entire world, rather we were born to change the world closest to us.