Characters almost unanimously matter more - or as much as - the plot in storytelling. Some readers are far more sensitive to characters than others, but most readers will admit how the characters in a story are written/portrayed matter in how much a story is enjoyed.
Some prefer odd, quirky, off-center characters and stories. Others prefer high-action heroes. Some like "sensitive", near perfect, gorgeous, wealthy, tender, or fragile. Others like rough, crass, or hard-edged characters. Regardless of what a reader enjoys, if enough readers don't invest their attention and emotion into your characters, chances are their interest in your story won't entice them to continue with your work. Some won't finish your novel. Others will grudgingly read the story if engaged in the plot but won't maintain the same investment and interest if they don't like the characters you've created.
One of my all-time favorite female characters is Sibella Giorello's Raleigh Harmon. She's an FBI agent who takes chances and at times plays outside the legal lines of her job, landing her in a heap of trouble but accomplishing the "necessary" in the process. She labors over her decisions in every area of her life, proves emotionally vulnerable to loneliness and stress over the psychological loss of her mother, what she believes was the murder of her beloved father, and the estrangement from her cold and distant sister. She loves God but often feels like a disappointment to Him and everyone else in her life. She's attracted to another agent but will not succumb to his "charms" or her feelings for him. She's complex, tender, tough, and humble. And I love to read the stories centered on her cases, her conflicts, and her sensitivities. In every novel from the first (seen below) to the latest (The Stars Shine Bright), more layers show up in her makeup. Sibella does a magnificent job of making Raleigh intriguing and desirable as a character.
Characters run the show. If they fail to be interesting, the "show" might close early and never get an encore.
Father, please continue to help each one of us who depend on you for every word we write. Apart from you, none of us could write a thing. Give us what we need to serve you the way you desire. Please. In the Name of Jesus, Amen.