Secondary characters aren't just support staff. The most useful ones are clones. These characters represent what might happen to the protagonist depending on the path they take. The three little pigs are clones of each other and represent the three possible responses to the same threat by showing the cost of each choice. Frodo and Gollum are another version of clones. Gollum is a warning of what Frodo could become if he succumbs to the power of the Ring.
This is showing at the structural level. Instead of having your protagonist tell the reader, "If I keep going down this road, I'll end up like XYZ," show them someone who already did. Let the reader make the connection.
Look at your secondary characters. Can any of them be clones representing the different paths your protagonist could take?