Great systems are flexible. They can adapt and change to the current environment in order to continue working well. Obviously every system has limitations but great systems are flexible enough to continue living on.
About 6 years ago a friend of mine’s dad found out that he had over 95% blockage in one of his arteries. What the doctors then discovered, was that his body (vascular system) had already begun creating a new artery around the blocked area in order to fix the problem. It was almost complete and resulted in him not needing surgery. That was a great system being flexible. Now most of us know of similar stories that went the other way (surgery needed), but even in those cases the vascular system still had to be flexible and adapt to new conditions.
It’s hard to change systems we didn’t create and fortunately most of the systems we may have to change are not God-sized in their complexity (like the human body). No, most of the systems we work with were man-made but still need to be flexible in order to be great. Because great systems work for a long time and most systems can’t go that long without changing in some way.