Your point was that all the characters have complex relationships to morality, and that their actions vary over the course of the stories. Further, that morality is subjective to each character, that fate/prophecy brings morality into question as it does free will, and blah blah blah. The sort of point kids should be able to make at primary school, and nothing like as profound as you seem to think.
We get it. But unless you think characters are binary "goodies" and "baddies" (which no one does), the linear spectrum allows us to weigh up all the conflicting actions and contexts, and make a nuanced judgment. Moreover, the fact that it's an individualised exercise allows the participant to incorporate their own subjective values, which can then be discussed as we compare results.
For example, for me, a sadist like Joffrey, Ramsey Bolton or the High Sparrow rates as more evil than Cersei, despite her presumably higher body count. I know that's not rational: it's subject to my personal distaste for the pleasure the first three took.