What are the disadvantages of immutability?

Could you elaborate on the downsides of immutability in the realm of cryptocurrency and finance? I'm particularly interested in understanding how this feature might hinder the adaptability and evolution of blockchain-based systems, as well as any potential security concerns it might pose. Additionally, I'm curious about how immutability affects the scalability and efficiency of these systems, and whether there are any workarounds or strategies to mitigate these disadvantages. It would be helpful if you could provide some real-world examples or case studies to illustrate these points.