I'm not sure there is enough room on MiceChat to list everything.
So, long list made short: It is the cause of every problem that exists at Disneyland. Probably most at DCA as well.
(Yes, this is hyperbole.)
Main specific wrong: It's too good of a deal for too high-quality a product, and thus is oversold, and thus is overutilized (more than originally expected). Thus lowers the average revenue per guest. Thus, this shortfall needs to be made up with higher day-tickets (thus making it an even better deal), cheaper-quality food/souvenirs at higher prices, and cheaper maintenance schedules. Slowly, the originally-high-quality product is cheapened to the level of the average gate revenue.