The script is hokey and some details are improbable (and I don't mean the supernatural ones) but the actors deserve a lot of credit. Someone among the reviewers here remarked that you can't properly act out a New Testament story if you don't believe in the New Testament; but after all, an actor in a ghost story doesn't need to believe in ghosts and an actor who plays Stalin doesn't need to be a communist. "Mary" has good actors capable of selling unusual situations. Even if their accents aren't coordinated.
Recent movies have milked the motif of the Chosen One for all its worth. This movie, although comes by that motif naturally, hammers a little hard at it, while also playing with the tired motif of the young woman who is anachronistically feisty in olden times.
I understand that the apocryphal Gospel of James and the Quran have Mary working in the Temple as a child. From this item of questionable history, the "Mary" movie generates a whole sisterhood of youngsters who belong visually in The Handmaid's Tale. The Temple, meanwhile, operates in tense coexistence with the Roman rulers, and that tension provides relevant and ample, if melodramatic, filler material for the script.
Joseph, who is sometimes thought of as elderly, is young and energetic here. Maybe not agreeable to all followers of the religion, but good for the movie.
What is this Mary movie trying to tell us? Does it have a particular spin to sell? I'm not quite sure. It spends quite a bit of time on Herod, and a little time on Satan as well, and my impression is that besides (of course) promoting the positive historical role of women and of men who respect and defend them, it wants to reassure us that in the battle between good and evil, those who defy the foul fiend will ultimately win out.