What is a poem?

I think too much poetry consists of jotted-down ideas. But these are just the ingredients of a poem. They are like the flour, sugar, eggs, and milk set down on the kitchen table to make a cake. They are not the cake. Jotting down the ideas is the first step in making the poem. The ideas have to be trimmed to skeletal form. A poem is a concentrate of thought. The peeled-back bared-down ideas  have to be connected, and then set in rough first-draft order. Then the metre and rhythm have to be worked on to express the thought appropriately. The language has to be worked on to fit well into the rhythm, and to match the over-all mood of the poem. The imagery has to symbolise the deeper messages of the poem, and the images need to  echo and reflect back on each other. They should stimulate visual, auditory, and tactile memory. The closing lines need to sum up, or point towards, the whole.
Otherwise what you have is prose arranged in short lines.