I mean, in a sense it is a free speech platform. The mods of any given instance can ban you, sure, but there exists no instance or higher authority in the network that can ban you from lemmy or the fediverse as a whole, even if every single instance were to hypothetically ban you at the same time, you could still spin up your own instance and host your account there. They could all defederate and stop talking to it, but they couldnt stop you from still posting there and getting seen by anyone else that wanted to join it or connect their instance with yours.