The comment was getting long and I didn't want to get into socioeconomic side effects, mobile, or other factors.
It's not all bleak. The internet is still built on a foundation of free and open technology. HTML, CSS, and JavaScript (aka ECMAScript), TCP/IP and DNS …
The best thing we can do is teach those things. Keep them accessible to as many people as possible and make sure they don't become forgotten arcane voodoo knowledge. Anyone can set up a website and share it with others. We don't have to depend on big social networks.
The biggest challenge is how do you get people to be curious about this stuff? Back in the day, we had to learn, we had to look under the hood, because half the time stuff just didn't work and we needed to figure out how to fix it. But today everything is hidden behind a shiny UI and most things just work. There's no need to look under the hood (if you even still can, and it's not some encrypted blob or compiled binary webASM nonsense).