Well, it seems we disagree. Honestly, I see the problem of AGI as the fairly concrete one of assembling an appropriate collection of thousands-to-millions of "narrow AI" subcomponents.

There may be other approaches that are significantly simpler (that we haven't yet found, obviously). Assuming AGI happens, it will have been a race between the specific (type of) path you imagine, and every other alternative you didn't think of. In other words, you think you have an upper bound on how much time/expense it will take.