I think, in general, with Prada's penchant for updating old-lady looks, you need a young face in the clothes to bring the dimensions together, to give the sense that you can have something from the past that can be all about the future.
But instead, in this campaign, we have an older model made to look younger, a false youth, trying to bring freshness to clothes, trying to make traditional materials look modern, and it's not working. The ingredients of the formula have been misjudged ever-so-slightly, and it's not a disaster, but it doesn't work its usual magic.
If you're going to use an older model, use her because she's a model and she looks older, rather than hiring a 'name' because supermodels are back, and then making her look like a unnatural approximation of a 21-year-old woman wearing older clothes. Just hire the damn 21-year-old woman, in that case.