There are so many things that can go wrong in a drama with a heart-tugging story, especially when it brings in an overworked trope to add to the pathos. But the writing never got sappy. Nothing was played for cheap thrills. The acting was spot-on, never descending into over-played or over-done pathos. In all the many ways this could have failed, it never did.
Park In-hwan is a master actor and always worth watching. His face is amazingly expressive and he provided a memorable character that you would love to meet. This was an Oscar-worthy performance.
Song Kang was gorgeous to watch in motion. It's hard to believe that he hadn't studied ballet all his life, but I suspect some of the magic in all the dance sequences is owed to brilliant editing. He played a wide range of emotions - exactly what you would expect from a young man grappling with family tragedy and finding his feet in the world. (No, I wasn't being cute with "feet"!)
The entire cast was first rate, and you will love all of them.
If you have a dream, go out now and start to realize it. You may need to look for a parallel track, like the eldest son, or figure out what really matters, like the youngest son. I was over 50 when I took my first calculus class. You can do whatever you want to! Start now!