I’ll acknowledge there was more to the film than that. In an era of Self Magazine and the most Narcissistic President Ever to Wriggle Out of a Highly Credible Rape Charge, I think people were moved by a story in which somebody lays down his life for another. I think the film had enough violence in it to keep teenage boys happy and enough (dumb and flibbertygibbet) romance to keep teenage girls happy, and it had enough grrrrl power low watt feminist liberation stuff in it to keep various ideologues happy.
But most of all, the story of the ship itself is simply a very powerful one. That last element is not to be dismissed lightly. In his An Experiment in Criticism, C.S. Lewis remarks of myth that it is a kind of story with a satisfying shape, like a vase or a tulip. It is a story that satisfies us independently of the way in which it is told. Some stories are entirely dependent on the way in which the teller writes. But some stories exist almost independent of the teller and can still move us even if the telling is bad. I think the story of Titanic fits the bill for Lewis’ description of a “mythic” story. It retains power no matter how much Marxist agitprop, James Cameron Big Think and so forth is larded on top of it. Retain the basic shape of the myth and you move people.