You'd be surprised at how often that complaint/question/comment is raised within the parks.
I may have my timeline a little messed up, but I believe that Disney was the first to create a Fastpass-esque system for a theme park. Other parks adapted the system as a "pay to play" system, while Disney kept it free. Fastpass+ is now so far from the norm that the average Disney visitor is used to that it creates an inherent problem when they visit the parks for the first time. Almost every other major amusement park in the country offers some version of an express pass that you have to pay for, but it's more or less unlimited usage. Hence why many Disney guests are upset that they can't buy something similar when they come here. There are so many reasons as to why Disney wouldn't be able to make that system work, and so many reasons that guests get upset with the FP+ system, but that's a different post in a different topic for a different day.