I don't know if the Android camera app is considered to use "Material" but it's massively unintuitive to use. It's not obvious at all that to see a picture you just took you need to swipe to the left. Nor is it obvious that the small shutter icon once you have swiped means "edit" or "refocus" or whatever.
Google's opinion seems to be "It doesn't have to be intuitive because you'll eventually learn it".
After you take a picture you can see that the picture is "stored" to the right. There is a little animation showing where the picture is going. I dont think its as hard to figure out as you are implying.
I know it's hard because I'm actually an iOS user who happens to own a Nexus 5. I only use the Nexus 5 for testing. About once a month I pull it out to show someone the re-focus feature. It almost always takes me several minutes to figure out where it is. Finding the camera app is easy. Figuring out how to get to that feature is hard.
Google's opinion seems to be "It doesn't have to be intuitive because you'll eventually learn it".