I agree: migrating a community is really challenging. I'm a subreddit moderator myself, and when we were initially discussing this stuff, there was a lot of doubt because of how daunting the task is. Mods from other subs see the challenges as reason to not even try. However, I think it's important that people at least make the attempt given the current state of Reddit.
Something that I think people should keep in mind is that this stuff is gradual and doesn't have to happen all at once, especially since the alternatives aren't fully polished yet. Even just establishing a small, active community outside of Reddit (like people have been doing with all these fediverse communities) is a big win.
Some of the best things we can do right now are
providing feedback and suggestions for alternatives
making sure alternatives are approachable (/m/quickstart is great)
simply being active and providing stuff to do here