Poetry changes when you memorize it. Rather than being a subjective observer viewing an inanimate object, you enter the world of the poem when you memorize.
Even just reading poetry aloud is better than reading silently — silent reading is a relatively new phenomenon. But memorizing engages reading, writing, speaking, hearing, and memory. Memory is one of our most complex powers and is interconnected with our other senses. Memorizing actually brings a poem to life.