I don't think it's always a matter of *needing* to update an opera so that the audience will understand it. After all, many people have a tough time with opera, now matter what period it's set in. Personally, I'm more interested in updating, not as a necessity, but as a valid artistic contribution of its own.
Handel's Giulio Cesare presented in ancient Roman and Egyptian garb can work very well for a modern audience (we all know at least something about Caesar and Cleopatra). But it also worked brilliantly when updated to the heyday of the British Empire, in David McVicar's already classic Glyndebourne production. Not because the director *had* to do so to connect with his audience, but because it lent a whole other dimension of intriguing historical parallels and resonances.
For all I know, a skillfully staged "traditional" production of Der Freischütz might work effectively for a modern audience. But even so, I'd still like to see Sacramento's fascinating alternative.