Heavily dependent on the circles one’s part of in my experience. Everybody I followed when I moved to mastodon several months ago (mostly devs, apple users, and a few designers) are still there, actively post, and have no plans to return.
Most artists I follow also just dropped Twitter entirely and are on Instagram exclusively now (much to my dismay, the Instagram UI is nails on chalkboard to me.)
I've seen numerous anecdotes from more technically-inclined types saying that their Mastodon posts not only get greater engagement than their Twitter posts did, but that the average quality of engagement is much higher and closer to an actual conversation.
So I can see a more intimate setting benefitting them more than a more traditional content creator who is already used to all those hoops.