Interesting points, just one thing I recently thought about: eMule vs Torrents. Torrents requires trackers and websites to host torrent files. eMule was rather fully decentralized from the start and you only needed the hash key. In actual performance there wasn’t a fundamental reason why one or the other would be better. But Torrents won by a large margin, and I believe it’s because it needed websites and trackers and created “hubs” that could fund themselves from ads.
This could similarly apply to the fediverse.
You might also underestimate how much moderation and how many malicious or fascists actors are under way. It could easily become a cesspool.
Encrypted DMs could be added later.
But I definitely think there need to be better tools for migrating your content. Or migrating a complete community including all posts from one instance to another (like a rolling journaling backup that you can do daily, and if your instance just disappears you can just copy it)