[Spoilers] Why Zenos is the most important character moving forward

[Edax]

My issue with the "Edax Test" is that it's not really a test - it's an assertion, and that can be challenged.

"Zenos killing the Warrior of Light doesn't advance the plot, therefore he is poorly written."
-Not necessarily...

What constitutes "good writing" and "bad writing" are somewhat subjective, so trying to apply an objective criteria to determine those is bound to fail.

Would saying that Zenos would be underwritten be more objective?