it seemed that most of the responders were employed by travel agencies or Carnival
Just by way of information, I don't know of anyone who uses this board who works for Carnival. There are 2 or 3 travel agents who participate. Looking through the responses, I see one part time travel agent and one full time agent who responded, but none of the other posters is part of the travel industry.
I'm sorry that you had a bad cruise, but luckily, you know which cruise lines and ships are a better fit for you and will sail those in the future. There is not a single ship that has ever pleased every single passenger who ever sailed on it. We have had discussions here about new ships with exploding plumbing, faulty electrical systems that led to no air conditioning and sometimes, no propulsion. Sometimes it's a persistent problem, sometimes the luck of the draw of which sailing you happened to choose.
I have no doubt that you encountered the problems you did, and won't sail the Holiday again. I'm sure your next cruise will be as enjoyable as the first three were.