I think the best argument against us ever finding AGI is that the search space is too big and the dead ends are too many. It's like wandering through a monstrously huge maze with hundreds of very convincingly fake exits that lead to pit traps. The first "AGI" may just be a very convincing Chinese room that kills all of humanity before we can ever discover an actual AGI.

The necessary conditions for "Kill all Humanity" may be the much more common result than "Create a novel thinking being." To the point where it is statistically improbable for the human race to reach AGI. Especially since a lot of AI research is specifically for autonomous weapons research.