The absolute best way to explain the fediverse is to not.
When I wrote a short guide to getting started on Mastodon I made deliberate efforts to completely ignore the technical side. The instance stuff does not need explaining. Nobody cares about that. They want to know how to find people to talk to on this Mastodon thing they heard about.
Nobody will tell you to try some chocolate by explaining the entire supply chain for all the ingredients that went into it. They say "try this delicious chocolate bar!" or words to that effect.
If you can't think of a USP for fedi that doesn't revolve around obscure technical details that most people do not and will never give a shit about, and that honestlly are kind of awkward to explain and sometimes even defend, well... I'd suggest going away and trying again.
Like, ultimately, I have no philosophical objection to Reddit charging for API access. I have an objection to Reddit a) charging ludicrous, unreasonable amounts with the very obvious intention of killing off third party apps and tools and b) repeatedly giving a middle finger to its own userbase, and particularly those who put in unpaid labour to keep the site ticking over.
Unfortunately a) goes against Reddit's express self-interest, and with regards to b) some people are stupid enough or salty enough about having their shitposts removed from places they shouldn't be to actually be on Reddit's side and going "yeah, down with mods!", neglecting to note that the mods are pretty much all that stands between Reddit and a horde of spambots, porn accounts, children, trolls and racists making the site downright unusable.