The difference with fusion is that we have a very good understanding of how fusion works, and exactly what we need to figure out how to do, to make it a viable energy source. It's basically just an engineering problem, albeit a very difficult one due to the extreme conditions. AGI is more like developing warp drive. With AGI, we really have no idea how the brain works or any clue of what problems need to be solved. It's basically just like the underpants gnomes.

Phase 1: Buying more GPU to increase the number of parameters in a LLM Phase 2: ??? Phase 3: AGI

AGI may come anywhere between next week, 1000 years in the future, or never. Anyone who claims to have any idea is full of shit, because we don't even know what problems we need to solve to get there. If we develop a good model of how human cognition works at a biological level, there is at least a direction, but that isn't going to be coming out of some AI hype factory with a datacenter full of H100's making videos of anthropomorphic cats working as pastry chefs.