It's possible that some concepts or tools can't be simplified or there's no point. Try explaining Webpack to an end-user. Such categories of things exist, in which case they are not products but components of other products. If Mastodon can't be understood simply, then it will only catch on with those who understand complexity, and be used in a product that is itself simple.
Mastodon is not that hard to understand. It's just not Twitter. It's not meant to be a 1-to-1 replacement for Twitter, but people keep trying to compare it to Twitter and then acting out like they're all upset because they don't find everything they're looking for in the thing.
If "Mastodon replace Twitter" is a thing, it will mostly be in the sense that people will be using their time differently, not that they'll be doing the same things as they do on Twitter. You're not going to "build a brand" on Mastodon. You're not going to make a name for yourself posting "dank memes". You're not going to get a chance to show off your "sick dunks" to your followers.
I think it's weird that people keep calling Twitter a "public square", but if that's how they want to think of Twitter, that's not at all Mastodon.
What is Twitter, actually? It's an advertising platform. It carrots people with celebrities and sticks them with promoted tweets. Along the way, some people find they can keep up with their friends, colleagues, and industry acquaintances through the thing.
Mastodon is just about the last thing.
Mastodon is software. It implements the ActivityPub protocol. People run Mastodon instances of their own to connect to other ActivityPub systems. There are other ActivityPub implementations, Mastodon is just one. It's not a platform like Twitter any more than WordPress is like the NYTimes.