Advertisers (and governments and criminals) pay handsomely for surveillance-driven "free" platforms, but who will pay for the development, maintenance, productization, polish, and support of open decentralized alternatives? Users have been conditioned to believe that software should be free, and the more ideological people in the FOSS movement will tell you it's "not open source" if you don't give it away with no strings attached. I know people who will actually uninstall things if they do not have an OSI-compliant license.
Look at how much work it takes to develop and maintain these centralized systems. Now consider that decentralized systems are more challenging to develop and scale because you have to deeply understand distributed systems instead of just hacking some code to run on one centrally managed 100% trusted platform.
Where is the army of independently wealthy highly skilled developers who are going to do all this unpaid?
I am not optimistic. Nobody pays for freedom, openness, or privacy. All the money and momentum is behind the current user-exploiting paradigm, and now we have a generation of programmers who are learning "cloud native" development and don't even know how to develop things that don't run this way.
Edit:
I once gave a presentation to a room of college kids and was discussing a peer to peer system. A student raised his hand and asked how two devices could communicate this way without "a cloud." He was not aware that it was possible for something to communicate directly with something else over a network without a server.