I'm not a fan of selective desat, but putting that aside while grading today. Instead, I'm grading overall composition and whether i feel like the item that is colored draws my interest or if i feel like it pulls my interest away from something else that i find more personally meaningful in the picture.
I love the textures in this shot and love the angles. This is truly a unique shot. But, in this one, the blue of the sky just doesn't compare to the texture of that wall. It does, however help to add context, by showing that above is a skylight that would be a bit harder to make out if the whole picture were greyscale.