I had bad dining room service on the Dream in January. And I've cruised
DCL several times (so know what to expect) and am not picky. It was bad. Drink server forgot about my drink order (after a direct order, not even expecting her to just remember my drink night to night), only saw the head server once in passing, dining server tried to give his menu spiel to two (unrelated) tables at once to save time, food routinely took a long time and was not really warm at one meal. The latter was at the end of the cruise and I was fed up at that point. I made him take it back (something I've never done before) for a new plate, and got a hot one almost instantly- it took me really complaining to get some prompt hot food for once. And no, I couldn't just talk to the head server about it, because he was MIA for most of the cruise.
The ship wasn't overcrowded or sold out, so this wasn't due to number of passengers (I've had good service on full cruises, anyway). It was just an incompetent dining room team.
The experience was bad enough to make me consider skipping the dining room entirely on my next cruise. I'm not going to sail the Dream again for a while. Hope the situation is better on the other ships. If it keeps being like this, I will stop sailing DCL despite finally becoming platinum. DCL charges way too much to offer Carnival-level dining room service.