I think we've narrowed down the point of disagreement. Since you agree that X and the Quests are inextricable, I'll try to build on your assertion that "Eunju refuses to accept the positive role Dice can play in the world".
This is actually very similar to an earlier discussion I had in Batoto with a person who said Dice could be used for a person to become intelligent enough to do something amazing, like curing cancer. (Being a Biologist, I cannot help smirking at the notion of "curing cancer"… but I digress.)
Let's see how this would play out. The sequence of events is more or less like this:
i. X gives Dongtae a Quest. To protect Dongtae's morality, let's say the quest is pernicious (they almost always are, to a certain extent), but Dongtae cannot see the evil. Let's say it is something seemingly innocent but which X knows will harm someone. Like asking Dongtae to steal Byungchul's notes (which is what got him brutally bullied afterwards).
ii. Dongtae fulfills the Quest. His consciousness is clear, because he cannot see the hidden evil, otherwise he would have refused it. X gives him Dice and Dongtae uses them to increase his intelligence.
iii. Rinse and repeat (i) and (ii) until Dongtae is clever enough to cure cancer.
Do you see what the problem is? Sure, Dongtae or anyone can use Dice to do good,
but said good is always achieved after an evil is caused at the moment the quest is fulfilled. And what's worse, greater rewards come with more horrible quests.
To be honest, I exaggerate the evil of some quests. Many of them are not evil, and protecting Eunju was definitely a virtuous quest. But that's not the general trend. The thing X feeds in most people are their basest desires.
What I am trying to say is that Dice - and here I disagree with you - are a tool of X's before they are of the Dicers' themselves. They are the tool X uses to lure them in. Without them, no one would have a reason to fulfill the Quests.
Only after the mischief is done can they be used for good. Ergo, for every good something bad has to be achieved.
That's the moral problem. What using Dice means is that before you can do good, you have to do evil (even if you don't know that). And that's what Eunju opposed when she first was told what Dice were. Those were the words of Gilma in chapter 23: "to get these Dice, people are hurting each other and treat others like trash". Only then did Eunju voice her "if that is the case, I think these things shouldn't exist." Clearly, she was linking Dice not with their potential for good, which is
ex post facto and uncertain, but with the virtual certainty that evil is accomplished in the process of procuring them… regardless of how well-intentioned people are.
I won't even discuss here the often overlooked fact that doing evil things changes one's mindset. For that, I refer you to a discussion of the matter
here. (I comment as Splicer.)
I don't think she will have a personal role in bringing down X. You are probably right, only a Dicer who can face off against him for the S-Rank and defeat him at his own game can do that.
But Dongtae won't do it as long as he fails to understand that Dice cannot be used for good while X controls their distribution. Eunju never issued a blanket condemnation of Dice, she conditioned (every time, in the discussion with Gilma and in the rooftop speech in the Long Day Arc) her condemnation to the way they are obtained.
This story, in my opinion, is about Dongtae arriving at the conclusion Eunju reached in chapter 23. But let's talk a little about Eunju's most controversial assertion, that earned her the most hatred from some readers. The one you consider "stupid".
In chapter 19, she was dismissing the notion of changing oneself. She believes in "working hard with what one is given". In a sense, this is exactly Taebin's, a veteran Dicer's, conclusion in chapter 67, isn't it? Dice or no Dice, the world won't change. There will be always people harming each other, having powers to solve some problems will result in other problems, etc.. So in this matter I am with Eunju, and it may be a philosophical difference between you and me: I do believe that working hard is more important. Because the virtue is in the working. It doesn't matter if you have an ESP power or not, but what you do with that power. Intelligence alone won't allow one to "cure cancer". Having the
motivation to cure cancer is probably a safer route.
And because Dice powers come cheap, most Dicers in the story are doing exactly what with their powers? What is constructive in what they are doing? Daewoong used Cloaking to shoplift. Gilma tried to use Psychokinesis to killl. Most of the time, Dicers are using their powers - because they failed to work hard to obtain them - not as a precious achievement to be used wisely but as a tool to… obtain more power. Even Dongtae hasn't used his powers to achieve much.
It's true that just ignoring evil won't stop it. However, understanding what the evil is is the first step to do that, and Dongtae has to stop thinking he can remain personally virtuous and benefit from Dice while X is in control. In contrast to Eunju, he fails to see the bigger picture.
The role of Eunju in the story, in my view, is
making Dongtae realise that.
And I am not talking about her lecturing him on the matter. But I wouldn't be surprised if Eunju's words on chapters 19, 23 and 34 spring to his mind when his contradictions come home to roost.
Even if her direct role is of a domino, something to make Dongtae snap,
Eunju sets the moral tone of the story. She has reached all the right conclusions, and Dongtae's duty as hero is to catch up. Her character is a "Mary Sue"
because this is a moral tale: she is the way the author says, "This is what I think is right." Beatrice in Dante's
Divine Comedy and Gretchen in
Faust play the exact same role: the role of being at the endpoint of the journey the hero sets out on. Eunju begins where Dongtae, I hope, will end. She is a finished product, someone who has attained enlightenment, and he is someone who needs to go a long way yet. That's why I like her, because she gives substance to the main argument. Without her, this story would lack a sense of direction, or it would all have to come from Dongtae's inner monologue… which would make it a little far-fetched, in my view.
Is it possible that Dongtae will arrive at a better solution than Eunju? A world where people actually benefit from Dice
and work hard with their abilities, without having to harm people to obtain them?
Perhaps. Then again, Dice are power in pure state… and power corrupts. Lord Acton tends to have the final laugh.
One final word: if back in chapter five, Dongtae had Eunju's fortitude of mind, none of this would have happened. Rejecting evil in the right moment
does make a difference. Taebin is on to something in chapter 22:
in a sense, this is all Dongtae's fault. Good intentions do pave the road to hell if they are not backed up by good sense. True, Dongtae is human and fallible, but so far he has not moved to set right his own wrongs.