...there is no facebook replacement. You can't replicate social groups via software. Facebook is not anything special other than most people use it, so the network effects are immense.

You could have the greatest software in the world and it would not be able to replicate fb's markets and groups functionality. Craigslist is the only one that comes close for replicating fb marketplace.

If you want a small private blog, just host a single user mastodon or pleroma instance. That way you're part of the fediverse but maintain control of your own personal instance.