I think it's mostly just that we are very good at picking up on patterns, and it's extremely noticeable that half the internet has started writing in the same voice with the same tics. If Claude were quietly posting away in 2017 I don't think anyone would think twice about its output.

We're well past the point where humans can reliably identify AI generated content. Sure, you might often correctly identify AI content, but part of that is due to how much AI content there is; you can call everything AI generated and still have a high ratio of correctness. Meanwhile, I guarantee there's a lot of AI content that you're failing to notice.

Rather than using the AI bogeyman, why not analyze things as-is? If it's good or bad, does it matter if it's AI or human? Or are you in denial about some existential fear?