I hope I can put into words what my puny brain is trying to compute ...
IMO, the whole FP system (with non-enforcement) worked fine on 75% of all attractions. FP and standby lines lines moved pretty quickly and things ran smoothly. Guests were in and out in a reasonable time frame.
The issue, however, was the remaining 25% of attractions where the FP system wasn't as effective. Unfortunately, these were the headliner attractions, such as Soarin', Toy Story Mania, Tower of Terror, etc. The demand for these attractions were so large that the FP's didn't work. Standby lines were horrible - up to two hours wait time. We were in a FP line for Soarin' and waited 45 minutes in a FP line. Another day, the kids waited 35-40 minutes in the FP line at ToT. Say what you want to about the standby lines, but you would expect FP lines to not be over 15 minutes - no matter how big the crowd is, or what holiday it is, or what special offers are going on at the time..
Personally, I would have liked to have seen Disney keep the FP system "as is" (with non-enforcement) for the attractions that the system worked on.
However, changes needed to be made on the headliner attractions to keep the times down for BOTH the FP and the standby lines. I don't know if enforcing return times is the answer or not. My instincts say that enforcement will help the FP lines move a little quicker to a small degree, but I'm not sure that will be any help to the standby lines.
Cutting down wait times for everyone needs to be Disney's goal.