Main Character and Protagonist

Some stories have a main character as the central figure:

Great Gatsby
Shawshank Redemption
Au Revoir Les Enfants

The protagonist in these stories is actively doing things but we don't see every step they take and sometimes don't even know their true goals.

Sometimes they are narrated by this character, sometimes not like in Au Revoir Les Enfants.

When analyzing these types of stories, I can't ask what the objectives and obstacles are because the main character, the passive main character doesn't have clear ones that act as steps toward a clear goal.  Their objectives are more episodic so to speak...but they do all add up in another way.  They are Observational Objectives.  Each scene must have an observational objective.  One in which the main character learns something new about another character or object.

So while the protag and antag are effecting the scenes in one way, this character is observing and learning.