> I'm on board with the usability argument, but I don't think that removing gradients and drop shadows necessarily results in designs that "scare users away."

He didn't talk about gradients or drop shadows, he talked about textures. Wood grain is texture, the paper fibers in most book pages are texture, ... There is such a thing as too much texture, but there is also such a thing as not enough texture: when there's no texture, the work feels dead, like holding a single chord forever.