I'm not sure how you define a blog. Could you clarify? I often delete or edit posts, so I have control. I download my FB data so I have an archive. I have a link to my FB on my Twitter and all my posts are public and I get people from Twitter reading it. I have 60 followers I don't know who read it. Not sure what else it needs to be to meet your definition of a blog.
I don't expect a free site to be available for eternity. That's why I archive it. The archive is a pretty nice format. I can load it up in a browser from an index file and browse my entire history. I could host it somewhere else if I wanted. I could use a parser to extract the content and repost it in a new format. I still maintain it is a blog.
That is not a blog.
You don't have control over it, you don't have archives, and it's not world readable.
None of what you listed is a reason to not to use a real blog.