Carnival owns a variety of cruise lines. I think most of their lines are pretty accessible to the average "walmart" shopper. That would be Carnival in America, Aida in Germany, Costa in the Mediterranean . The price points of these cruises offer great value to average people.
Carnival also offers some more prestigious lines for more affluent customers. Princess...Cunard...etc.
For an average family, who wants to go on a quick and easy vacation...Carnival offers a value to them. I work in a port town that hosts vessels and also has endless port calls from many cruise lines. I have seen worse debacles than these...but the media didn't get ahold of them. And Carnival has had debacles that didn't make the news.
This is just a news cycle. It will pass. But I think that Carnival and its customers will gain from these lessons.