My uneducated guess is that Princess, as a business model, has decided to deal, in part, with the inevitable disappointed generated by the unmet expectations of 4000 odd guests due to overcrowding and scarce-by-design resources in two ways: 1. Implement the compulsory use of a dining reservation app that is unreliable and inadequate and designed to thwart the attempts of its guests to the end that the quest can now be blamed for his or her own dissatisfaction and not the Company (you, guest, failed to understand the functionalities and limitations of our app and are therefore to blame for the absence of reservations and not Princess Cruises), and 2. Generate a stream of revenue over and above the base fare by offering onboard products and services design to alleviate the anxiety generated in tactic number 1 (Reserve Dining, The Sanctuary, Specialty and Casual Dining, the dozens of other things that require an additional fee). Both the disease and its cure, so to speak. Dis-satisfaction in a seller's market is the way to maximize profits, not satisfaction.
But this is all conjecture, I admit. As I sail shortly on the my first cruise onboard a Princess ship I look forward to the lived experience required to report back candidly and honestly and ruthlessly.