To most people (99% ?) Facebook, Instagram, Google etc offer everything they want. So they do not feel a need for getting the 'power back'. It all comes down to perceived (!) value. Once people use one thing, they will only switch if something else offers a clear higher value. At that point offering the same value is not enough anymore. This higher value has to be something that makes every day life in a very obvious…
Where the change will come is when we are no longer dependent on paying for network access. That will be the financial incentive. A fully decentralized web would be delivered peer-to-peer via a mesh network or something similar. Anything else is a farce, because it's not just about who holds the data on the network, it's about the network itself. If any link in the chain of the communication can be controlled by some…
I remember to have seen a protocol for such ad hoc mesh networks that wasn't even IP-based and could be implemented on most routers. The network can dynamically self-configure, route around failures, and nodes can go in and out of existence whenever they want. It looked pretty cool but unfortunately can't remember where I've seen it. :/