No, I don't think planning is a waset of time. The future is not always unpredictable. I think we tend to remember the times when it is unpredictable rather predictable. Most things happen as we plan and as we believe they would. The things that surprised us are what stand out. This is not the norm, it just feels like it is because it is a stronger memory.
Since the future is not determined and can be unpredictable at times, planning is great but we need to remain flexible.
Planning allows us to move forward when things do occur in a predictable way leaving us with a bit more resources in the event something unexpected occurs.