I am pretty black and white with my ratings
I either really like the drama : 8.5 - 10.0
or
I don't like it : 2.0 - 3.0

There is no in between except for 1 or two dramas. If I don't like the dramas I would just drop it and often don't rate it unless the dissatisfaction of certain plots and acting stuck on me then I will rate it.