Discussion Backpacking Without a Plan: Too Risky or Ultimate Freedom?

My 20-year-old son and his friends are planning a backpacking trip to Europe for the summer of 2024. They're considering going without a set itinerary, arguing it'll give them the ultimate freedom to explore and experience the continent. I'm a bit concerned about the practicality and safety of this approach. Has anyone here backpacked without a plan? How did it go? Were there any major challenges or unexpected benefits? I'd love to hear your stories or advice to help me understand if this is a doable adventure or a recipe for disaster.