I will probably be flamed for this but: I don't blame the cruise lines I blame the cruisers.
People accept mediocrity and if they accept it then the cruise lines will be more than happy to give it to them. It increases the bottom line and that makes management and the shareholders (large shareholders) very happy.
I too have found that overall food quality has dropped in the MDR and buffets of most ships and cruise lines. The food you once knew is now served in the alternative dining venues and the cruise lines are making money off of these venues.
Cruise passengers, who will eat whatever is put in front of them as long they don't have to cook it or wash the dishes, must preserve that $399 inside cabin price and walk off the ship with an on board bill of $23.95 are what have caused the decline in food quality and the decline in service.
I have no real problem with that on most mass market lines. There has to be broad based appeal but I see it happening on the Premium (or whatever they are called this week) lines. When Celebrity opened the Olympic on the Millennium it was truly a culinary and service experience that was more than worth the surcharge. The Pinnacle Grill was also a special place but now they are what the MDR once was with a little better cut of beef.
You get what you tolerate.
A number of years ago there was a thread where someone wanted a "Cracker Barrel" type of restaurant instead of the fancy MDR. There was a lot of support. I knew this was the beginning of the end.
On most cruise lines I often eat more in the alternative restaurants than the MDR because I want the dining experience I had five to ten years ago. I can have meat loaf at home.