I wouldn't ever use an LLM for my own writing. But I'd use, after edits, for letters to bureaucrats, landlords and other types I'm forced to deal with.

The thing is, the author may care about Linkedin but the relationship that many people have with linkedin is as a place they have to be. "Hmm, I need a blog to enhance my career but writing, urg. I know just the thing...". Which is to say, it's not strange Linkedin is going to be filled with crap. None of my actual friends on Facebook post crap 'cause there's no incentive.