Increasingly this just seems like fantasy to me. I suspect we will see big changes similar to the way computers changed the economy, but we will not see "capital as we know it become basically worthless" or "the modern economy and society around it collapse overnight". Property rights will still have value. Manufacturing facilities will still have value. Social media sites will still have value.
If this is a fantasy that will not happen, we really don't need to reason about the implications of it happening. Consider that in 1968 some people imagined that the world of 2001 would be like the film 2001: A Space Odyssey, when in reality the shuttle program was soon to wind down, with little to replace it for another 20 years.
I was with you on the first two, but the second one I don't get? We don't even have AGI right now, and social media sites are already increasingly viewed by many people I know as having dubious value. Adding LLM's to the mix lowers that value, if anything (spam/bots/nonsense go up). Adding AGI would seem to further reduce that value.