I think a better of thinking about this is that, sometimes, evolutionary processes falls into a local maxima or a local minima. There is a trick in the wording of, “The better adapted you are, the less adaptable you tend to be”, since “adaptation” was redefined in the second part of that statement. If you’re so well adapted to the current situation such that you fail to adapt to future, hypothetical, unknown situations, then what you’ve really done was to hyper-specialize and stop responding to change. This is not that one adapts too well so much as one got comfortable and
stopped adapting.
In terms of practice, it means someone stops being mindful of the task on hand and starts performing his tasks mindlessly. The present moment is always surprising, this principle of adaptation is not.