I'm usually a big fan of the EFF, but it's wrong on this one. If you decentralize to the limit -- i.e., such that each user is running their own instance for themselves -- it becomes okay for the service to become liable for the user's speech because the user and the service owner are one in the same. In reality, (extremely) federated social media is the only kind that can survive without Section 230 and thus repealing it entirely would be a win for the Fediverse.
(You could argue "but users won't go to the trouble of running their own instance," but to that I'd say "they will if the law doesn't give them any other choice, short of not participating at all.")