The newest movement by many cruise lines is to hire well known chefs, with great reputations, to redesign their ship's menus (not just the physical menu, but the food they servce).
For at least the past 12 - 18 months, I believe the food on those lines is improving, rather than waining.
They do have their work cut out, as I do believe that for the previous decade many of the lines had worked harder on making cut backs, and making them work.
At this time I think many of the cruise lines are actually refocusing on their food departments. They still have to work within budgets, but I do think we're seeing the bounce back in what they are serving.
But, no one should think it's possible to serve 1000 people at a seating, and make the food as good as in an initmate restaurant where all the food is cooked to order. All the food in the MDRs is pre-cooked to a degree, and salads, soups, etc. are prepared before hand.
A large ship can not pick up enough fresh products in the majority of ports of call to supply their needs. So, all meats and fish (for example) are frozen until needed, and they stock enough to last the duration of the cruise + extra to be sure.
On a seven day cruise, the ship carries enough stores to last at least 7 days. They can't take chances.