I don't speak for others, but yes I can navigate from locked phone to messages and type a full message to my wife without looking at the screen, thanks to qwerty knowledge and GBoard's "swipe" typing.
For example, if you have an app open in a folder, you'll have to press the home button 3 times: once to exit the app, another to exit the folder, and a third to go home (unless the messages app is on the dock, then you can press twice to reach it).
I'd be worried about messaging the wrong person, and I also have fat fingers so that's no help :(