After finishing the first episode, I could tell why this was rated so highly: It's very heartwarming. It is sweet and inspirational watching an elderly man find passion in something late in life and prove to the world that he can do it despite his limitations or what anyone else may think. Yes indeed. But that alone isn't really what makes a drama "good" or necessarily watchable to me.
I continued through episode 4 and felt pretty bored. There's not much more to this drama IMO than excellent production value and that heartwarming-ness it has going for it. Plot is very slow. Wasn't for me.