They are going to have an adventure. And within a few days, they are going to sink into the Atlantic, but not into oblivion. R.M.S. Titanic became a legend on her maiden voyage by simply hitting an iceberg and going down with two-thirds of its passengers. Because there's so much story to tell, we don't really get to know any of them, although we care about them all in the way that we have feelings for anyone we know is doomed. That chill of destiny carries Titanic through its first act, but the stage Titanic's problems become evident in the second.
All drama needs conflict, a protagonist, an antagonist.
The show's creators have rightfully kept the focus off the characters and on the liner. There are a couple very big somethings missing here. Despite the absence of the show's real stars, Titanic is fun to watch with its huge cast, all of them capable, most of them anonymous. The show's most noble characters are its working stiffs. The weakest sections belong to the millionaires, but everybody is dressed to the nines, so at least you can admire the costumes while waiting for something more interesting to happen.