Propaganda and censorship are attributes of the same underlying aspect: monopoly. Centralised control.
Both problems have the same effective solution: break up the monopolies.
Propaganda is a function of amplification, attention, audience, selective promotion, discovery, stealing the air supply or acquiring of any competion, and coöption of the platform. Propaganda is an inherent property of centralised control.
Gatekeeping and censorship are functions of excludability, audience gating, distraction, negative selection (obfuscation), stealing the air supply or acquiring of any competion, and, again, coöption of the platform. Censorship is an inherent property of centralised control.
Audiences, a public, divided across independent networks, with access to different editorial selection, with access to different input message streams, are far less subject to either propaganda or censorship.
Or of surveillance, whether of the state, capitalist, or non-state-actor varieties, which is also an inherent property of centralised control.
It's importance to realise that the key is not nominal control but actual control, which may be nonobvious or unapparent to many participants. A system with appearances of decentralisation may well be centralised under the surface.