PieFed allows you to block all users from an instance of your choice without needing admin approval. The Lemmy apps Sync and Connect do also. So I’ve already managed to defederate from Lemmy.ml personally, aside from lemmy.cafe, dubvee.org, or quokk.au that have all done that at the admin level.

Although it sounds like you meant more that so many communities are still on that instance - which is fine - and don’t have alternatives yet elsewhere, which is not fine. If you can, perhaps consider making just one and modding it to help it grow. It won’t fix everything but it will help, and if 9 other people did likewise then that’s 10 communities that people would not have had access to without those group efforts:-).

Little by little, I think that we don’t have to consider places such as hexbear.net as part of “us” anymore. Perhaps it will take the further development of Mbin, PieFed, and Sublinks to accomplish that for Lemmy.ml. Otherwise we simply will progressively give up while the place dies slowly around us, as people leave and new ones refuse to join.