Curious - is your concern that the post is 100% AI generated? Or do you object that AI may have been used to clean up the post?
It also leads to slop spam content. Writing it yourself is a form of anti-spam. I think tools like grammarly help strike a balance between 'AI slop machine' and 'help with my writing'.
And because they are so low effort, it feels like putting links to a google search essentially. Higher noise, lower signal.
I found Grammerly to be often incorrect, but it's been years since I tried it. I use LanguageTool instead, simply to catch typos.