You're right about that. Dealing with astroturfing will be an arms race and will require some proof of "humanity" in social media, forums, etc.
But, ultimately, I don't buy the idea that astroturfing is all bad. Or the opposite, that the lack thereof is necessarily good. I think bombarding with AI content can have possitive effects, like overwhelming human moderators who built echo chambers and ban wrongthink (e.g., Reddit). Or, it has the capacity for a small organization to compete with the likes of the NYTimes, or The Atlantic, etc which currently control the narrative.