Without characters there would be no stories. I suppose one could use an object to tell a story. Tried that once with a park bench but those were in the days when I was finding my way as a writer.
Often rejections speak of the poorly developed characters, or that they are cardboard. How does one solve this. There are four areas to help in developing a character.
Social - There are universal traits. Is the character male or female, child or adult. There are certain things common to each of these areas. Where was the character born? This country, another country, in the city, a small town, a rural area. There's a difference between characters who were born in NYC, in the Kentucky mountains, or a Texas ranch.
Intellectual traits - What kind of education did the character have? Are they curious or not? Where did they go to school? Did they drop out, have a dozen degrees. Do they have a profession and how did they choose it?
Emotional traits -- How does the character react to a situation. Wgat are their feelings about where they live, about their looks. How do they react to pain, to pleasure, to friends and enemies. These traits are sparked by the emotions.