There is no excuse for bad preventative maintenance. That seems to be the case with them. They almost wait till there is a problem before they address it. Now sometimes things just go wrong and there was nothing they could do to prevent it, but it seems the issues are too frequent and many may be preventable. They just canceled another 10 sailings and extended the dry dock of one of their ships. If there was nothing wrong they would not have done this.
Carnival does have a long history, but that does not excuse its recent actions. The problems seem to be the result of a large company trying to increase its profits by cutting corners and getting caught doing so. A company that tries to cut back on the passenger's experience for its own gain is a bad cruise line.
As someone who was recently on the infamous carnival cruise line where dookie was running down the walls and the power failed, I can say with confidence that they are an absolutely abysmal cruise line. It is no coincidence that they have had a string of high publicity failures of their cruises.
Carnival has been around a long time, long enough for it to be clear that their current stretch of misfortune isn't the norm for them. Unfortunately for them and those that have stock in the company it's been so rapid fire that everybody will think they're truly this bad, but history says no.