I suppose that means be prepared for human waste spilling in the hallway from a plumbing blowout with repairs taking days. Or, a burst water pipe flooding yours and a dozen other cabins in the middle of the night. These and other such events happened on Volendam during its recent South America Grand Voyage - I was there. All are related to the age of the vessels. In both cases full repairs were delayed by not having repair parts on board. As the chief engineer explained, there is no store of these obsolete parts. They require fabrication.
Among the more mundane, newly installed drink dispensers in the Lido go unused for reasons unknown. But, the carpets have just been refreshed, protected by numerous buckets catching the drips from the ceiling. I say these things after 74 days aboard Volendam, and a week aboard Zuiderdam that was so bad the CD apologized from the stage. These ships are each over 20 years old and their mechanical conditions show every year of it.
People come here looking for honest answers to their questions, not "It's all great" when it's not. Right now, based on my very recent 81 days of combined HAL cruising, I say it's not. That said, if the itinerary is what the poster is drawn to, ignore the ship's shortcomings and spend time enjoying the places one will visit. (BTW: We will be aboard for this voyage out of Boston in '24. We have our eyes open and expectations set accordingly.)