A decade of reinforcement and agentic learning was spent playing games (Google Deepmind AlphaGo, AlphaStar, OpenAI Five), including against each other. So what makes it a new frontier?
The difference is going to be instead of starting from pre-existing games and hoping that "generalizes" to intelligence, this time people are going to build gamified simulators of economically valuable stuff. This is feasible now because we can use LLMs to help generate these games much faster than we would have been able to previously.