The consequences of a new thing being invented are not entirely dependent on progress of innovation in the thing itself. It takes quite a long time for people to build _on top of_ a new technology. LLMs could not appreciably improve at all, and we've still barely scratched the surface of applying what we have.

Your car example is a perfect one -- society was _completely reordered_ around the car, even though the fundamental technology behind the car didn't change from the early 20th century until the invention of the electric car.