The Indieweb helps with this. With the Indieweb:
With this system, users own their own content on their own websites without trusting silos to host content for them.
This is a very incomplete solution: expecting everyone to run their own website and go through the onboarding process for the Indieweb is laughably unrealistic, and having one place (centralized or decentralized) to see multiple people’s reactions is useful. It is only a solution for a subset of people and use-cases.
Also worth noting: most websites with regularly-updating content (blogs, Twitter, even YouTube) have RSS feeds; full-text feeds can be another great way to preserve content.