People who are like "The migration to Mastodon has failed!"

No it hasn't. I literally migrated to Mastodon from Twitter, and I don't use Twitter anymore, but I do use Mastodon every day.

I call that a successful migration.

@rasterweb I consider it successful also. I am quite happy with the diversity and breadth of my follows here and the conversations. I've learned a bunch from other folks interesting posts and replies.
@stepheneb it's successful in that there's enough content and conversation about subjects that I'm interested in to serve as a social media platform. I don't have Twitter to compare it to, though