I almost hesitate to get involved in this discussion because I do not wish to ruffle any feathers, nor do I wish to insult anyone. If I do I apologize now before I start!
These are my opinions, and mine alone.
QE2 was built because, at the time of conception, the bean counters at Cunard Line LTD., thought that they had a way to make a vast amount of money. They did. They threw everything into it that they could, to save operating costs, maintenance costs, increase crew efficiency, increase passenger satisfaction, speed up service to passengers etc etc. While still keeping the Cunard BRAND ( I capitalize because this is important!) They did their sums, got ideas from a vast amount people around the globe, both in the hotel industry and from a technical standpoint. Some of those things were small, some huge, eg aluminium superstructure.
Things did not go well from the get go as we all know. Turbine troubles.
Lets face it QE2 was state of the art!
I think that QE2 was built either 10 years too early or 10 years too late!
Over the years and various management changes it slowly went down hill. Service dropped because money to provide that service dropped, had to keep the profits up, without spending too much to do so. Other cruise lines were coming out with newer products, more "gimmicks/amenities" and all QE2 had was what was old by say....1976. Remember, once a ship is built it is very difficult to rebuild her! Very few, if any, ships are planned/built with rebuilding in mind. Think things like Penthouse suites/ magradome, deck buffets, USPH an additional 1880 tons of A/C capacity.
Enter new management, that to be honest, had absolutely no clue as to what the Cunard "Brand " was and what their goal market was. They tried to merge the markets using the same food and same entertainment, all the time cutting costs on them.
Now bring in new ownership changes and the whole ball game changes. Some of them for the better, some for the worse.
Add to that, QE2 was getting older, had been pushed hard for the first years of her life and it was starting to show. They change itineraries so that there would be a hard push to the first port then a gentle cruise to the next couple and a hard push home. Drydockings were changed to every 2 years and refurb budgets were cut. Some refurbs were done at sea, like carpeting, curtains and upholstery. Half of the work for an annual refit was done during the 4 day call at Hong Kong. More time at sea where the money was made.
All this time QE2 was being "updated" bit by bit, to try and get the younger crowd, with more money onto the ship. But this was driving the older crowd away. Which was fine because they were dying off anyway. Cunard name recognition was waning, even during my time at sea the name Cunard and QE2 was becoming less recognized! Then they did a big refit don't know when, after 89 trying to put the old style back. Kick out the formica etc and put wood paneling in, restore the old Cunard. Looked beautiful. But a little bit too late I feel. I also got the impression that whomever the ownership was theirs hearts were just not in it.
I think they finally said, look we have an expensive white elephant here that is going to start losing lots unless we rebuild. What do we do? You have your answer.
So, I do not think it was SOLAS, Carnival, management aluminium. I think it was an all of the above.
If you are going to drive your 1926 Rolls Royce every day for 400 miles at 50 mph, be prepared to have to put more and more money into it.