We might simply not be able to comprehend our own brain to a level that let use emulate it. The toys we're playing with today aren't even remotely close to emulate any kind of intelligent animal, the best we can (almost but not even fully) do is a worm with 300 neurons [0] (vs 80+ billions for the human brain)

Technocrates told us we'd have AGI and flying cars by now, I'd stay cautious about people claiming reaching AGI is a question of time alone.

[0] https://openworm.org

OpenWorm has been stalled for like half a decade now too.

That said, there's a huge difference between "the brain may be too hard for us" and "the brain may not even be physical." That's about on the same scale as the difference between "the pyramids were built with advanced mechanical tools" and "the pyramids were built by aliens."