One common problem among writers of all styles and genres is a protagonist who is passive rather than active. Things happen to this character, and they react to their environment and generally get pushed around by life. Or things happen to other characters in the novel and the protagonist comments and witnesses but isn't necessarily involved. I have seen a lot of unpublished (and a few published) novels where the supporting characters are more interesting, rounded and alive than the character who the book is supposed to be about.
I think that one possible reason we might write protagonists like this is because, as writers, we've become used to taking the role of observer of human behavior. We watch what happens and think about the lives of people and then when we pick up our pen/tablet/notebook/keyboard/whatever and write, we place ourselves within our protagonist and then make him more-or-less into us, an observer. This is perfectly natural, because in a large way it's what readers do when they pick up a book. To read a novel is in many ways to pretend that we are the characters in the book. It's one of the things that gives fiction its enduring power: the opportunity to safely sympathize or empathize with someone unlike us, in a dramatic situation.
But we have to remember that our role as a writer is not the same as our role as a reader. We don't get the luxury of sitting back and seeing what will happen, and neither therefore does our protagonist. We have to drive a wedge between our perception of the story and our protagonist's perception of the story, build a wall, and get some critical distance from her.
I think that another reason we sometimes write passive, observer or (worse yet) victim protagonists to whom things happen but who doesn't make things happen, is because we think that the best protagonists are characters with whom we can readily identify. So we try to write heroes who are essentially us, or people just like us. This is a mistake, because you and I, to a large extent, do not lead dramatic lives that lend themselves readily to interesting narratives. No, we don't. I don't, anyway, at least not anymore and thank all the gods in all the heavens for that. But I digress, as usual. To make up a protagonist who is just like you is a tactical error (though I'm sure you are a perfectly lovely person and we should have lunch sometime, soon). As I said above, the enduring value of fiction comes from the reader's opportunity to live vicariously through and safely sympathize with someone who isn't like them. Readers come to your work seeking to engage with it, seeking commonality with your characters even if they don't know that's what they're doing. So unless you really are an action hero, don't make your hero someone just like you.
How do you know if you have a passive protagonist? I suggest the following exercise. Read the first 50 or so pages of your manuscript. Make a list of every time something happens to your protagonist (each time they are a victim of an event), and make another list of every time your protagonist acts to change something. If there are more "victim" events than "act to change" events, you've got trouble. You can also just sit down and look at each scene and see if it's a scene about your protagonist trying to change things. Stories are about change. Stories are narratives that explain how a new status quo was developed by an individual, and why that change was necessary. That's a story. (It is true that some stories are about how an individual failed to make necessary changes in the status quo, but those stories are still about action.) Either way, the protagonist acts. The protagonist acts in every scene. If your protagonist is asleep, your reader will be.
So the point here, or one of the points, is that you as a writer have a role that is vastly different from the role of a reader. You do not sit and see what happens next. You MAKE WHAT HAPPENS NEXT OCCUR. And so does your protagonist. Because nobody else is going to do it.