The follow up to Plato's Poetics, is Aristotle's Poetics! Aristotle's Poetics has often been hailed (especially by Aaron Sorkin) as the most important piece of literature for understanding and writing narrative form!
If you want to understand basic story structure, this is the place to start!
https://www.stmarys-ca.edu/sites/default/files/attachments/files/Poetics.pdf