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

[Edax]

There's a big difference between the Bechdel Test and the Edax test. The Bechdel Test was never intended to be a measure of the quality of a work, by the author's own admission. Its sole purpose is to illustrate a TREND in writing, in works both good and bad. The implication being that it's far more common to find a "Hamlet" in literature than a "Hamlette", as it were. What this trend actually means is up to interpretation; certainly there are no shortage of individuals quick to point out how it might relate to "the Patriarchy", or what have you.

The Edax Test is VERY MUCH intended to be a measure for the quality of a work, and stands by the principle that any work that utilizes a certain trope MUST BE BAD. That there is NO WAY to take that particular literary formula and construct an enjoyable and meaningful story from it.

You misunderstand, the Edax Test is a meant to be a measure of the writing. Perhaps it would be better if I edit my signature even through this results in me committing a double negative.
"Can the Antagonist progress the story if they destroy the Protagonist? If the Antagonist cannot, then they are not well written." The Alien in Alien is barely written as it remains largely an unknown, but it is not necessarily a bad antagonist, just not a well written one. The Alien in Alien is appropriate for a horror movie, but what makes Ash so great is that Ash is a well written antagonist. And we know full well what would happen if Ash, and by extension The Company had won because it was a detailed part of the story.

While I haven't brought it up before, it may well be the case that NOT EVEN ZENOS qualifies for the Edax Test. Can Zenos progress the story if he kills the Warrior of Light? Certainly he could! In fact, we know exactly what he would do, if he were to overcome his worthy foe. It's the same thing he did when he overcame his tutor: Seek out a NEW worthy foe. In fact, wouldn't it be a hoot if he decided that a grand contender for the position of next-worthy-foe could well be the foes who've been giving his PREVIOUS worthy foe so much trouble? I could easily see Zenos taking his battle to the Ascians themselves - or if he felt truly ambitious, he might assist them in their plans so that he could take on Zodiark himself. There's always a bigger fish - but Zenos is not satisfied with that. The Hunt continues until he is the biggest fish of all.

One could argue, "Nuh uh, that won't happen, if Zenos won he'd do X!!!1!" until one is blue in the face - but we don't know. And we never will know, because, for obvious reasons, Zenos isn't gonna kill us. If this was a work of literature, however, and not an MMO, What Comes After would depend on the talents of the writer, not some arbitrary rule.

The reason we can argue until we're blue in the face is because Zenos is not well written. His motives are so simplistic that Zenos can't function on his own because he's not a fully formed character. His motivations are vague apart from his single fixation, take that fixation away and he'll be vague again.

Zenos might fight the Ascians, but we he wont do it for any reason related to the story. Again I have to stress that FFXIV is not a fighting anime and we are not in a tournament arc, Zenos seeking the strongest opponents has nothing to do with the story. The fact that there are some strong figures in the Light vs Dark storyline does not mean the story is at all related to Zeno's hunt.

Now tropes aren't always bad, but they aren't always good either and the tropes that Zenos imbues harms the story. Zenos pulls the "Not So Different" trope when he claims that he and the Warrior of Light are the same since both want to taste the blood of their enemies in battle and it falls completely flat. Zenos is clueless, he has nothing of value to say as he knows nothing about the WoL and thus he does not even care about the Warrior of Light despite being a creepo stalker. A villain monologue that has nothing of value to say is just wasting time. We all already knew that stalkers are bad, we didn't need 2 expansions dedicated to a stalker whose unrelated to the core story.