Next to the "tiny preview rectangle," there's a gray arrow indicator that suggests swiping right. If you do that, you'll find a button you can tap for the old functionality.
So now it's tap-swipe-tap instead of just tap, but in exchange the old functionality of sending an existing photo has changed from a long series of actions to just tap-tap-send.
Now all you get is this tiny preview rectangle at the bottom. It doesn't launch a full camera so is useless for most cases. That's why I have to open the "real" camera app and take the picture and come back.