Writers barely saved viewers from depression

This show was awesome up until episode 13, to the point where I could give a 10/10 on every episode. I think extending the show by 2 episodes had an effect on episodes 14-18 significantly, to the point I was basically raging and depressed by this last episode. How did Yong Pal fall from a genius, take-matter-into-his-own-hand doc to this passive emotionless idiot?

Thank god the writers put in a decent ending, though literally up till the last minutes of the drama, I was prepared for the worst. It's so unfortunate a drama of such potential had its high point in midway through, not at the end.