I see people saying that have had similar experiences on other lines, and I don't doubt it. I am sure Disney has it's bad days, and I am sure other lines have their good days.
However, I judge from my personal experience. My father used to teach classes on the cruise industry and when he was doing research for his book I had the opportunity to be his personal errand..... um.... to tag along...Yeah.... so I have sailed at one time or another every major line. Granted that was MANY years ago and I am sure a number of them have worked hard to change their images. That said, I have never had an experience on another line that I consider as good as I have on a Disney ship. Carnival I don't like. I will say that flat out. Don't even get me started on MSP. However I consider RCL and NCL to be "good" cruise lines. I don't think they do 'bad' by any means. I just don't think they put the spit polish on as well as Disney does. However, that's to be expected - RCL and NCL treat their ships like hotels. Disney is clear that their ships - just like their parks - are stage shows. It's just how they have and always continue to do things. They are less tolerant of disrepair, dinginess or unkept areas.
As I said - just from my personal experience. I know others will disagree.