Off the grid network
So decentralised relies on old world tech. What if we reuse old world tech in a new way to essentially make a new network using low-tech methods souped-up with new technology.
LoRa
There exist such a thing as Long Range radio communication, so called LoRa. These devices are not specifically expensive and therefore can be used by private individuals. You could have a software defined radio setup where you push signals that get relayed and distributed by these LoRa devices.
Mesh
The network would consist of multicast/anycast messages. Meaning they would go into the void and only with a target and anyone who receives the message and it is not for them re-transmits it. If it is for them they consume it. The payload can be encrypted with public-private key pairs in order to limit the amount other people can see. They might only know these two entities talk to each other but have no idea where they are. They can of course send messages but the other party cannot decrypt them yet as the necessary information has not yet been propagated.
Flaw
The flaw in the design is the payload and the data that can be transferred. Although it can be effective at small data payloads like chats and such it will not succeed at all at things like websites and other forms of applications/services. Transferring some large files cannot be done at all. The other flaw is the fact you have to share with people in real life the keys or through some other medium before you can communicate. This is fine for social circles but not for communication that is similar to what happens on social media now.