I don't doubt some people have run into issues with Mastodon, like not being able to follow accounts because of defed, but I doubt it's as prevalent as the criticism makes it out to be. It's also a wild as the same is literally true of Bluesky, like there are Bluesky accounts you have to jump to Blacksky to view because the CEO of Bluesky got her feeling hurt because she didn't like being criticised for hosting transphobes who break the site's own rules.