Enterprise crew discovers a planet suitable for having a shore leave. But like all the encounters by the crew, this one became an adventure of discovery.
The planet is surrounded by a technology of hologram (like appeared in TNG) or illusion (like in the episode of Cage) which is unknown to us; the Keeper of the planet didn’t share that information. Even he said, “you’re not ready to understand us”, which might be a litmus test to evaluate species like testing pre-warp societies.
Like Captain Kirk is tired at the beginning, the producer might be tired after 16 episodes. We don’t know. But at least this is one of the inspiration points of holodeck technology, which will be discovered later.
I don’t want to dig the clues more, because the episode seem like an amusement-focused one, and the details, except the mandatory ones for the story development, has been cut.
One takeaway: Greatest the mind, simplest the games.