Sadly, you aren't correct. For our cruise to Hawaii this year in March. We had purchased the plus package when we originally booked this cruise. Before the cruise Princess changed the Plus package (I think they adjusted the casual dining). Sadly shortly after we got off that cruise, the changed again (I also think in regards to the casual dining). I understand the OPs concerns. Sadly, this can happen, and the cruise line get's to make that choice.
DW don't cruise often, but when we do we cruise Princess. We really enjoy the product. We often try to take advantage of things so that we don't have to worry about anything on our cruise.
That's why on our next cruise we are trying the Premiere package.
Everyone is different on what they want for their experience, while the cruise line may change things, you still have choices.
Hoping for all the best for you and this dilemma.