Literally, my Grandma uses Mastodon! It is not hard! Many of us are old enough to remember a time (before gmail became the de-facto standard) when we had to hand-hold non-technical friends and family members through the process of choosing an email provider. Choosing a Mastodon/Matrix server is pretty much the same thing. Once you have an account on the server, there is pretty much nothing no downsides even for non-technical users...