"Control" here means that there are people who write blogpost worthy comments or messages on Facebook or other Meta properties. That's the only place where they exist.

When Meta (or any other company) decides to destroy them, they go away forever. You have no "control" over it.

https://indieweb.org/POSSE is the way to go.

You want to write a long post on a 3rd party platform? Write it on your own device, that you control. Then you save it, copy the content and post wherever you like.

If your 3rd party blogging or social media platform goes tits up and everything disppears, you still have your own copy you can just Ctrl-C Ctrl-V anywhere.

You can go as fancy with this as you like, depending on your nerd-level. You can have a self-hosted N8N system that automatically reposts everything to new sites you add to the flow. Or you can just have your stuff in a directory in Obsidian.