Plato illustrated the box as a prison
Plato illustrated the box as a prison in the form of a cave inside a mountain. The prisoners are chained behind a wall. All they ever see are reflections on the wall of a fire that is operated by the keepers of the prison, and some shadow images produced by the keepers. But one day, one prisoner brakes the chains, climbs over the wall, and instantly recognizes that the shadows that they all saw, which defined their world, was an illusion. In time the prisoner notices the exit from the cave, and finds a great wide world outside that he had never imagined to exist.
When Schiller laments that society too often fails to respond to the great opportunities before it, he laments in a sense that too much of society remains imprisoned by its small-minded, captivating, and often intentionally cultivated, illusions.
Obviously, if one is psychologically imprisoned into a science that disregards 99.999% of the universe as if it doesn't exist, one lives in a world of fairytales where extremely little is actually real.