A lot of vloggers do seem to use sony mirrorless an not care about the flip screen. They do have decent face tracking autofocus so that might be more important to them. Casey Neistat would use Sony for his studio videos and Panasonic for vlogging because of the flip screen. He switched back to Canon though because Panasonic's contrast detection autofocus is limited.
Blackmagic's idea is that you grip the camera and use the thumb button to record. And with your index and middle finger you can press the exposure button and the focus button located on the back. That doesn't seem like a great solution.