My question was specifically about "the general non-technical population". Do you expect my mom to even remotely understand what different servers are and why talking to me is securely encrypted but talking to her friends group isn't? The point about secure software is that it needs to be secure by default or else, entry level users will manage to accidentally send their stuff in plain text and not even notice.
For nerds like us, I agree that Matrix is probably a good choice. For someone who needed to be told that "the internet" isn't the blue "e" on their desktop... not so much. I'd rather send carrier pigeons than explain Matrix to my family.
I wouldn't be surprised if there was a whole generation for whom loss is the "hide some lines in your posts" meme and who have never even seen the original comic let alone know who Tim Buckley is.