With respect, a lot of the questions you ask are quite naive.
Software system issues are commonplace in our society, and the idea that Disney should somehow be immune to the effects of our entire society's increased reliance on technology makes no sense. Many companies have had software system issues in recent years, and in some cases such failures have resulted in hundreds of deaths, and in other cases exposed millions of Americans to identity theft and other forms of fraud. A few hours delay getting into a theme park pales by comparison. If anything, the fact that the problems Disney has had with technology have been comparatively infrequent and inconsequential is what is notable, but of course that rarity and lack of severity of issues is perhaps why so many people are so quick to go off the rails and blow every little problem way out of proportion whenever there is an issue.
Incidentally, just because it doesn't include the provisions you want it to include doesn't mean that Disney doesn't have backup plans. It is one thing to expect triple-redundancy when people's lives are at stake (Read:
Boeing 737 MAX) or when you're responsible for safeguarding someone else's sensitive private information (Read:
Equifax Data Breach), but to expect that kind of redundancy to keep a bar code reader operating is irrational. SMH