Well that’s kind of baked-in to social media. If you’d otherwise talk to lots of different people in person, read much etc and now come to the internet and choose any of the mentioned platforms… That’d be bad. You’re now in a smaller filter bubble. If you’re already in some echo chamber and for example switch from mastodon to bluesky… that’s a minor change. The situation is a bit different if you change from a nazi platform to a regular one. It’s still not good. But better.
I think because true communism never existed. All the previous attempts were flawed, people got corrupted, misused their power and it’s difficult to overcome human nature. It might work in theory (or not). But so far the attempts
weren’t that many and theywere all flawed for different reasons.