Basically, since we hit the 21 st century, all sorts of companies putting all variety of customer loyalty/rewards programs in place has become very common.
The cruise lines all pretty much jumped in; some offering different incentives than others... but then what "rewards" are of value to people is their personal view.
From what I can see from these program changes, they have basically increased the number of days/cruises necessary to qualify. I frankly don't see any additional rewards added for the continuing loyalty.
It seems now their explanation is that their program has proved too successful, so they have to react by cutting back the numbers of people qualifying for the "rewards"... and telling us, watch out, if that success continues, we'll have to cut back again.
Truly, not all that big a deal to me, but I think their problematic reaction has mostly been caused by them. The eventual changes were touted by John Heald for quite some time; promising how happy they were going to make everyone.
In the end, the changes were simply taking away "rewards" people had "earned" with their loyalty according to the earlier rules the cruise line had set.
The big mistake was promising great things, and the reality being quite the opposite. I am amazed how long it took for them to decide on their cutbacks to the rewards.
Other than extending the number of cruises necessary to get some of the rewards, the only thing they seemed to add was F in VIP.