I think that his statement highlights a misunderstanding of the capabilities of ML in the near future. It's an honest mistake since all the startups chasing pumps in investment are selling the idea of terrifying power.
A more apt parallel, in my opinion, is that of solar geoengineering. We are doing what Oppenheimer wish we did: ignore its existence. However, the allure, now as it was then, is that it's too little effort for too much power to ignore. It isn't an existential imperative to the global North so it has been dismissed. Make no mistake if climate change posed a direct and immediate existential risk to nations of the global North we would have stopped global warming already. Instead we are waiting for the collision of "nations that can afford solar geoengineering" and "global warming posing a direct and immediate existential risk" in 2-5 decades and doing none of the legwork to avoid unintended consequences because the notion of doing the science is not popular politically.
Fortunately we are all pretty far away from an existential war. That's the only thing keeping us alive after Oppenheimer's grand success. Even if a nation crumbles the things that replace it need to at least offer the trappings of a legitimate state if they don't wan to be immediately crushed by nuclear superpowers (assuming they themselves are a nuclear superpower or adjacent to one).
So the cutting edge isn't what's physically most effective, but what's most effective while also being within the gray and constantly shifting "acceptable" range. It's nice that we don't have to go all out, but as soon as scarcity or existential threats enter the picture things can get very ugly quickly. Best to steer clear of such things if possible. I consider chemical, biological, and weather weapons all in the same class of "you better not if you don't want to start a world war".
A more apt parallel, in my opinion, is that of solar geoengineering. We are doing what Oppenheimer wish we did: ignore its existence. However, the allure, now as it was then, is that it's too little effort for too much power to ignore. It isn't an existential imperative to the global North so it has been dismissed. Make no mistake if climate change posed a direct and immediate existential risk to nations of the global North we would have stopped global warming already. Instead we are waiting for the collision of "nations that can afford solar geoengineering" and "global warming posing a direct and immediate existential risk" in 2-5 decades and doing none of the legwork to avoid unintended consequences because the notion of doing the science is not popular politically.