While true, there are projects which surmount these hurdles because the people involved realize how important the project is. Given projects which are important enough, the bots will organize and coordinate. This is how that Anthropic developer got several agents to work in parallel to write a C compiler using Rust, granted he created the coordination framework.

I think the difference now (in case code quality is solved with LLMs) is the cost of effort is now approaching zero.

This might be true today, but think about it. This is a new scenario, where a giga-brain-sized <insert_role_here> works tirelessly 24/7 improving code. Imagine it starts to fork repos. Imagine it can eventually outpace human contributors, not only on volume (which it already can), but in attention to detail and usefulness of resulting code. Now imagine the forks overtake the original projects. This is not just "Will Smith eating spaghetti", its a real breaking point.

I'm equal parts frightened and amazed.

I mean in 1850 I kept hearing heavier than air flight was just a year away, and yet here we are without heavier than air flight...