Exactly! That's the great thing about the whole concept of Federation; it means that if you don't like how a community is moderated you can make your own on a different instance. And if you don't like any of them or demand even more direct control, you can spin up your own instance.
Same problem as with any social network migration: the network effect.
Sometimes the largest equivalent Lemmy community for a subreddit is tiny, or worse, nonexistent. Sure, you can go create one, but unless you can also convince other people to join with you, it won't be much fun.