> AI, brain science and cognitive science are extremely difficult fields with small advances, yet people assume that it's possible to 'brute force' AGI by just adding more computing power and doing more of the same.

Do people assume that? I mean, I'm sure some people do, but I don't think I've encountered many people, at least not in the AI safety movement, that actually think it's a matter of more hardware power. Some people think it's possible that that's all that's necessary, but I don't think most will say that that's the most likely path to AGI (rather than, as you say, actual breakthroughs happening).