Disney is making plenty of money off of food and beverage sales. If there was a problem they would be rethinking their pricing strategies. There is not a problem. As it stands the resorts and parks barely have the dining capacity to keep up with demand.The people buying food don't always pay full price. Disney uses pre-paid credits, package and passholder discounts to encourage people to eat on site and demand for table service dining is certainly not equally spread across property.
And the bulk of park guests are not eating at table service restaurants. They're the ones in line for places like Pecos Bill and one of the most common criticisms of Disney, from even the most casual of visitors, is that the cost of food is too high. It's why so many guests opt to get groceries and why this policy is now in place. This new fee does nothing to address that concern, and is simply a short term fix to a problem Disney themselves created.
Epcot is the third (soon to be fourth?) most visited WDW park. It has 17 table service restaurants with three more on the way, 11 quick service locations, and countless windows/carts around the park. And yet they still find ways to ever increasingly fill the park with more venues to sell food and beverage at even higher price points as part of festivals. Yet somehow all those locations remain economically viable. Disney (and it’s participants) have no trouble selling overpriced food and beverage.
People have been bringing groceries to their WDW vacations for decades. When I visited with my family in the 80’s each trip included a stop at the grocery store or a prepacked suitcase of snacks, quick breakfast items, and beverages to have available in our room. This is nothing new. This is not because of the ever increasing food prices. This is because new services and technology have made the ordering easier than ever and those who are ordering are lazier than ever. If you want someone to brink your case of water all the way to your room you should expect to pay for that service.