It took me years of begging and pleading with my wife to start using signal, the setup for which is way easier than matrix. I don't think I'd be able to get my wife to use matrix due to the increased complexity.
I have secure comms with my wife (albeit centralized) and that's what's important to me.
Yeah I think these luddite people would be better served if they took a more free/libre (gnu, fsf) approach to computing vs rejecting technology wholesale.