On the "All Hands on Tech" podcast, Mat Pancha did a review of Mastodon.
It's seems like he's not a big fan.
Specifically, he doesn't like that Mastodon isn't conducive to passive zoning out. He wants a service you can use without thinking.
However, to me, the appeal of Mastodon (and the Fediverse) is that this is social media that requires you to turn on your brain.
Mastodon is a bicycle for your brain.