I wonder what it is that is keeping more diverse users away?
The more diverse users are the ones that aren't realistically worried about their online privacy and are too used and comfortable with what the big names offer. They're more likely to be the ones that would only move once "everyone they know" moves.
Also, consider that the "advertising", the message and reason for joining the fediverse, It's like [Twitter/Reddit/Instagram] when they were good, minus the corporate meddling and greed and algorithmic shit shoveling!
, only really catches the attention of a few types of people.
Average Joe and Jane won't move out, "there's nobody there (that they care about)". Internet famous Joes and Janes won't move either, because they will lose a significant portion of followers.
People are willing to put up with A LOT of shit to avoid moving out of places like Instagram, Twitter, Reddit or Tiktok, since the time spent there makes them feel like it's a place where they belong to.