Genuinely one of the best questions I've read on this topic. That dives deep.
AI Paid placement is on it´s way and the signal gets corrupted the same way PageRank did. Google without ads was actually remarkable. Clean, almost pure. Then the business model ate it.
AI without paid influence is the same window. Right now it's open. How long nobody knows. As we all know in the backend, the full development is proceeding. We will see what arrives on stage...
You missed the point with your LLM generated response.
SEO ruined Google keyword search 2 ways. First by causing an arms race where Google tried to de-emphasize shitty content, and SEO morons tried to work around Google. Second, by providing repetitive, content free garbage that wasn't what anyone wanted to know. Ruined the web, paved the way for advertising to ruin everything.