Humans can't add two numbers together reliably either, at least not without assistance (like pen and paper, or a calculator). We invented calculators exactly because humans are not innately good at such calculations, so I'm not sure what you think this proves.
> If you're looking for the actual AGI breakthrough, look out for some qualitatively new and interesting way to connect these brains together.
All of these are being and have been connected to LLMs now, to great effect. See RT-2, for example.
Finally, I think you vastly overestimate human capabilities. LLMs are already superhuman in many tasks. Adding a "few more intelligences" where they currently fall down does not at all seem far off.
This has been my experience so far: people underestimate the capabilities and rate of progress in machine intelligence, and they often significantly overestimate human capabilities to derive their estimates. Overestimating human specialness has a long history.