> By that standard, centralized social networks have utterly failed us as well.
They're not on the same level; moderation of social networks like Twitter/Facebook can be considered insufficient, but it exists. Contrast to the very low barriers (if any) to send spam emails, where the filter is, ironically, in the hands of centralized services like Gmail.
No, the filter is in the hands of everyone who runs a mail server. Gmail et al. run the most centralized spam filters, but anyone running their own MX will almost certainly run their own spam filter as well. Likewise, Mastodon moderation falls to the servers.
They're not on the same level; moderation of social networks like Twitter/Facebook can be considered insufficient, but it exists. Contrast to the very low barriers (if any) to send spam emails, where the filter is, ironically, in the hands of centralized services like Gmail.