Payment processors underpin ad systems and they have strong leverage to pressure ad buyers and can pull your ability to make those sales. That's on top of the advertisers themselves having strong positions on what kind of content they want to advertise beside.
Everyone has to pay for servers somehow. Especially at scale. And doing that without payment processors is difficult. Crypto has not proven itself to be something consumers will use.
In all reality, the solution to as much free speech as possible on a social platform is to limit reach. If people want to broadcast to millions or even billions, then of course that will come with limitations and restrictions. Everyone has to balance the varied interests required to achieve scale. Limiting individual reach means more potential freedom for users.
Even in a federated system, you can be blacklisted although it does take more coordination and work.
i2p and writing to the blockchain are an attempt to deal with that through permanence, but those are not without their own (serious) problems.