Plato banished poets from his ideal state primarily due to their failure to apprehend and represent the higher, transcendent reality, focusing instead on the sensual and illusory aspects of the physical world.
This perspective aligns with Plato's theory of Forms, where he posits that true reality consists of abstract, perfect Forms or Ideas, and what we perceive through our senses is merely a shadow or imitation of this higher truth.
Plato believed that poets focus on imitations of the physical world, which are mere appearances and not the true reality. He argued that poets lack the philosophical insight to grasp the eternal and unchanging truths of the Forms.