Am I off base to view this as a strong hint AGI won't arrive through mere LLMs?

There have been strong hints since the 60s.

Probably not.

LLMs might be a step towards AGI (assuming that's possible) but the prevailing belief that LLMs and human brains (the latter being the most complex structures in the universe that we know of) are already functionally equivalent in every way that matters seems more like an article of faith to me than fact.