There are millions of Twitter accounts in Japanese, but if you don’t follow any of them, and nobody you follow retweets them, you’d never know they exist. You can also block or mute specific accounts, mute keywords, etc for even finer control.
That's not at all true by default; you also see tweets from people that have paid for involuntary reach for the tweet (promoted tweets), tweets that people you follow have interacted with, tweets that respond to or mention people you follow, and probably others that I'm forgetting.
Agreed that Twitter isn't a message board, but that's a much closer analogy than calling it a phone call.
If that was true, that would help a lot.
Well, Twitter is Twitter. But Twitter is probably closer to a message board than it is to a phone call.
But those boards are moderated by people who are part of the community. Not by the software nor the software host.
Twitter, FB, Google are not part of those communities. If they want to be cesspit of spam and trolling they should be free to do so.
When you post something on Twitter, unless your account is private, you've broadcasted your speech to anyone in the world who cares to see it.
Not moderating any speech at all is a quick way to allow a community to turn into a cesspit of spam and trolling. Look at any web board or forum over the past several decades for inspiration. They either have moderation, or they get overrun.