It's kind of impossible for a character not to have a goal or motivation. You say he's only doing what he does because of a rule- surely there's a reason he follows this rule? Even if the character wants to just exist, that's a goal. You should be throwing hurdles at your character in order to have them act towards their goal, whether their goal is for things to stay the same or change.
Now, a passive character is a different thing. They may have a goal, but things in the plot just happen to them instead of them doing things that affect the plot. For example, a character wants to go home after being lost, and are passive in the sense that they just run into things in the plot. Like they walk around and the say, evil scheme unfolds as they just kinda wonder around and they're thrown into fighting because they're told to. A non passive character in this situation might go looking for a particular person, strike a deal, and decide to take on the evil scheme to save their home, fighting to keep their loved ones alive.
Like honestly there's nothing wrong with a passive character if it's done right and serves the story. I've said before that the main character of my comic is extremely passive, that is, until about the halfway point where he begins to act. My character is in a cult where his goal is just to stay there and have nothing change. He's dragged around by the plot and other characters because it makes sense for his character- he's a kid that seeks guidance from other people. His character arc is him learning that being complacent and letting these things happen to him is not what he wants, which changes his motivation in the comic from staying to trying to escape. People like him as a character because I've shown how his abusive home life has led to him accepting any love he can get. And also- having other characters that are significantly less passive helps here as well.
Again, it depends on the story. But usually I'd say it's good to have a character taking action, because what they choose to do and what lengths they would go to achieve their goals can inform a lot about them as a character. Seeing why they want this is important to.