A coaches system is not exclusive to the offense or defense that they run. It also involves how they relate to players. The WCBB landscape has been changing at an excelerated rate on many levels and in many area's. This is not just in the level of skills that the players bring out of high school but also their attitudes.
John Wooden, some time after retirement, once stated that he would not be able to coach that present crop of college players. Pat was an old school disciplinarian. With her it was her way or the highway. It was not just her technical approach to the game that was going out of style but her relationship to her players. The choices available to players today in respect to excellent coaching and top programs has increased. Along with an increased level of Prima Donna attitudes our to high school, most players are less likely to put up with a Pat Summit approach as they were during her day.
It was not so much that Pats coaching ability declined, rather the level of coaches around her got exponentially better. She was competing against coaches like Vivian Stringer, not only in recruiting but also in the NCAA's. I am not criticizing her coaching style. I think there is a lot to be said for it, but it was one that could not be sustained as the WCBB landscape changed. One only has to look at the increasing amount of transfers taking place.
In respect to her adjusting her offense moving forward, I am not as convinced as you that she would have done so. Her strength in coaching was her force of will. Her do it my way or no way approach. That was a major part of her personality. It is aspect of her personality that also makes her less adaptable. Does anyone really believe that she would mimic or copy anything that Geno did? She wouldn't based on principle alone. Even though the early stage symptoms of AH might include rigidity , that was already part of her personality so it does not follow that it was what kept her from changing her offense. A persons strength is usually also their weakness.