Uh, if you're on wifi or a mobile connection, depending on the configuration, it pretty much is exactly like shouting a private message across a room
I could press a glass against the wall and listen to people having a private conversation. Does that make their conversation public "like shouting it across the room"? No. Of course it doesn't.
Get your analogies straight.
I could use my zoom lens to spy over your shoulder as you type your message into your super-encrypted phone. I will now publish the video on youtube, your private message now public. Serves you right for "shouting your message across the room".
We live in a world where eavesdropping on a private conversation is possible because people aren't talking in a cone of silence every time they want privacy. The unlawful intent to listen in needs to be there, and then some sort of action is required to hear the conversation, such as holding a glass to a wall.
Exactly the same with digital messages. Sure, they can be listened to, but not by just anyone accidentally, as the video seems to suggest. Unlawful intent is required, and specific actions with specific software to listen in.
I'm all for encryption, but let's get something straight: unencrypted messages are not dripping down the walls for anyone to read who passes by.