Ridley Scott’s “Alien” was so wonderfully efficient and succinct that it needed no further elaboration. Unless you’re a Hollywood studio that likes money, in which case you recruit a parade of mostly hapless filmmakers to expand on its world. All of them produced completely inessential results—including James Cameron’s passable “Aliens,” a success only in that it wasn’t particularly bad. So Scott himself deserves credit for returning to the franchise with actual ideas to explore, first in “Prometheus” and then with “Covenant.” With these films he’s set up a genuinely interesting creation parable, an ambitious story of the irresistible pull of playing god. The problem is the ideas are barely perceptible amid the haze of thuddingly obvious plotting and irredeemably stupid characters. “Covenant” is at least modestly more competent than its predecessor, but there’s not a minute in this film that feels at all surprising.