Conflict
Stories need more than elegant prose, they need conflict.
A typical modern story begins very briefly on a status quo – the situation for the protagonist is 'stable' at least on the surface – maybe not perfect, maybe not happy, but the power-dynamics are what they are and unlikely to change..., until they do.
An inciting incident disrupts that original status quo, creating an essential conflict that can't be ignored. The protagonist can't continue how things were, their stable situation is lost.
Suggestion: Quickly introduce an inciting incident that creates a conflict the protagonist can't ignore, and can't immediately solve. In story terms, this is probably THE big conflict that seems impossible.
Character Desire and Stakes
At this point, not before, we begin to learn who our protagonist really is.
Before the inciting incident, everything was settled. If they are fortunate, their daily life was pleasant and secure; if unfortunate, their daily life was not their own to choose. Either way, now that the status quo is broken they will start to question their goals and what they are meant to do.
Do they attempt to hold on to what's left of their normal life, or do they seize the opportunity to actively steer the plot? Are they cautious, or adventurous?
Suggestion: The stakes should be suggested from the situation and the character archetype, but the roleplayer should be allowed to pursue their own desires within that framework.
If the roleplayer begins as a thief who is in jail suspected of murder, the character desire is presumably to escape or appeal, and the inciting incident makes this possible. Maybe the player is presented with a jailbreak of cutthroats – out of the fryingpan into the fire.
Maybe the roleplayer is a princess forced into a political marriage, but the inciting incident casts doubt on loyalty, or the ogres are at the gate and the wedding party must defend their lives, or she goes through with the marriage only to consolidate power while she can keep it.
Present the player within their opening 'normal' (presumably the starting scenario you've all agreed to). The inciting incident breaks that normal, and should be a chance for the player to give their character agency and signal what direction appeals to them.
Character Need
One thing is certain, they can't do 'nothing'. There is an immediate need that must be handled now – a mini-conflict that demands action. The current situation is not open-ended, and the player loses agency because they are forced to react or adjust their behavior. They must respond.
A gamification way of forcing engagement is to add a 'ticking clock'. The ship is sinking and on fire, but horrified cries means people are trapped below deck. It's nothing to do with the character's longterm desires, but everything to do with what's happening right now.
Screenplays differ from novels in their requirement of 'scenes' taking place between characters at a time and location (novels can fall out of coherent time as the author drifts through stream of consciousness). I suggest your roleplay will work better with discrete 'scenes' which include other characters to help steer the story.
A classic screenwriting essay is called "Do your scenes turn?" by Robert McKee. The broad idea is that the story changes direction in every scene. Whatever your conflicts and sub-plots, the whole purpose of a scene is to witness a moment when the story 'turns'. The protagonist uncovers a truth that makes her distrust. Another character hints at an ulterior motive. Something un-predictable screws up the plan.
There are no scenes where the protagonist is allowed to enjoy the view, or just exist. There are always external forces, and specifically other characters that are de-railing the protagonist's serenity, needing an answer to this conundrum.
These short-term conflicts and character turns should be pre-scripted, and the story should steer the player toward them.
Antagonist
Antagonists are story elements that block the protagonist's progress.
In roleplay terms, they are probably story boundaries rather than mini-conflicts. The conflicts invite the player to engage, whereas antagonists need to signal they are immutable.
The ship is on fire and people screaming below decks is a conflict. It is very different if the protagonist decides to save the cat or kick the dog.... But the ship is sinking and the water is rising is pure antagonist – nothing the protagonist does can stop it.
I think it's natural to write what is appealing: the power fantasy, the sexy romance, the dark edgelord saga.... But successful stories treat their protagonists unfairly, allow them to fail, and railroad earned progress. I'm not sure that's the goal with a roleplay novel.
Probably best if your antagonists play 'fair', by somehow signaling they are structural, or world-building, or uninteresting, rather than a mystery to solve or a conflict to engage in.