It is a human failing to criticse and complain (glass half empty). Nothing in life is perfect and a small problem can be magnified with hind sight. First cruisers, who have no comparisons to make usually enjoy their cruises. People who have enjoyed 'traditional' cruise ships find the more casual approach disappointing. Some people expect the same standards on MSC (really good value if you like that sort of thing) as on QM2. It's not going to happen, is it? Bad reviews get loads of responses, good reviews rarely get any.
I thought about your question, unless someone responds and says yes, after I read the negative reviews, I booked the cruise and after I got home I criticised it for the same reasons as previous passengers because............. I don't think you receive an accurate answer to your question, because at present, we do not have the ability to look into the minds of others so we can only infer their reasons. Possibilities may be, reviews are only a matter of personal opinion, so there has been some exaggeration in the negatives (also applies to positives) the proposed cruise is at a different time, or for an alternative itinerary so some previous negatives will not be applicable. Not cruised before or not on the same category of cruise so will not experienced the issues personally. Expectations, I have heard many times, good and bad, the cruise was not as envisaged, a passenger wasn't sure what to expect, but it wasn't this. An another issue may be circumstances, only cruise within specific dates or budget or as someone commented in an earlier post haven't actually read any reviews, am going with an open mind, only to return with same positives and or negatives as previous passengers. Sorry I can't answer your actual question, hope you find the above suggestions helpful and someone else will provide some alternative ideas.