If you need to blame someone or -thing for the cheeseball internal rhyme in the title, then you can blame my WIP. It's busy glutting itself on alliteration and internal rhyme, the muddled slob.
But, as I was saying, one of the best ways to add complexity to your works is to draw from multiple sources. Have a strong main character (MC) but translucent (and not on purpose) supporting characters, or the opposite problem? Have dialogue in which every line gets a tag because everyone sounds the same and you can only tell them apart through a complex system of color-coding? Have conflict that dwindles at 1/8th the length you were aiming for? Sounds like you need some depth.
You know that 12-foot brass urn of Shiny New Ideas rocking in the corner? Reach in and pull out a handful of scenes and bits of internal monologue and that terrible villain who haunts your dreams. Fuzzy up the sides a bit and slip them into your WIP. Do they fit? If not, why not? What about your world makes them impossible?
Of, if they fit, where did they come from? What do they want that's so far outside your other characters' hopes and dreams? Where do they intersect, and what happens when they do? Your characters all want to find out what happened to MC's father. That terrible villain with one white eye just wants someone to own up to putting a dent in his Veyron.
And voilà, conflict is born and depth begins.