I totally respect that you mostly enjoy the cruising itself, and all that the ship has to offer.
But the business model and the promise is different.
Princess themselves on their website (pages "new to cruising") present cruising as, in that order, the travel ("best of destinations", "waking up in the morning in the world's most exciting and interesting cities"), then the value (that includes gastronomy, entertainment and activities).
As I've written before, unexpected and unavoidable changes are acceptable (last summer it happened to us in the fjords due to storms in the North Sea).
Ditching two highly interesting ports for two very secondary ones months in advance (7 in my case) isn't. And I should be offered the possibility to change or cancel the booking.
Actually, I should be informed to start with (I haven't received any email so far).
I'll nevertheless certainly enjoy the cruise and also certainly not check Princess' offer when I look at booking my next cruise. I'll let them know why. I strongly believe in the consumer's power. If we all stop buying their product, they might adapt their conditions.