One thing that can help elevate a character from mundane to interesting is to make them active. What I mean by this is they should actively be making decisions to move the plot forward, be an active participant in the story of their lives.

In contrast, an inactive character is one who sits by while things happen to them. They are reactive instead of proactive. Other people make things happen, and they simply go along, reacting as needed. They complain about problems but do nothing about them.

I once wrote a character like this by accident, early in my writing career. Beta readers told me she was whiny. She made little effort to change her circumstances. It would have been fine if she'd tried and failed, because at least she would have been attempting something. But complaining and doing nothing is just annoying.

Readers want to root for someone. People tend to admire those who take initiative. Heroes don't sit on the couch, waiting for trouble to knock on their door. They go after their destiny.

As part of your character's personal journey, they can go from being inactive to active. They can start the story helpless and hopeless, but maybe someone shows them or convinces them that they can make decisions and move things forward. By the end of the story, things are better because of things your character decided to do, and not other people's actions.

There are some exceptions to this, usually in comedy. If you've ever seen a Mr. Bean movie or one of those old Mr. Magoo cartoons, then you know what I'm talking about. The character unwittingly bumbles into situations and comically bumbles out of them all while being completely unaware of what's going on. This type of reactivity is hilarious, and not what I'm talking about in this chapter.