As they say..."the only thing that stays the same...is change". Very specifically spelled out in the C&A language that the program can be changed at any time.
When we started sailing with Royal, there were no Pinnacles...no Emeralds. There were no Diamond Lounges, no Suite's lounges....just the concierge lounge that allowed GS pax and above in ....and Diamonds and above in.
Then the Diamonds were kicked out of the CL...now the D+ are kicked out of the CL on ships that still have them. D+ never allowed into the newly created SL. Now Pinnacles not in a GS and above can find themselves kicked out of the CL or SL.
So yeah, angry Diamonds were kicked out suddenly with no notice some years ago. But they are not the only ones affected.
And so it goes.