1. Biological brains are non-differentiable spiking networks much more complicated than backpropagated ANNs.
2. Ion channels may or may not be affected by quantum effects.
3. The search space is huge (but organisms aren't optimal and natural selection is probably local search)
4. If it took ~3.8b years to get from cells to humans, how do we fast-forward:
* brain mapping (replicating the biological "architecture")
* gene editing on animal models to build tissues and/or brains that can be interfaced (and if such interface could exist how do we prevent someone from trying to use human slaves as computers? Using which tissues for computation is torture?)
* simulation with computational models outside of ECT (quantum computers or some new physics phenomenon)
Note: those 3.8b years are from a cell to human. We haven't built anything remotely similar to a cell. And I'm not claiming that an AGI system will need cells or spiking nets, most likely a lot of those are redundant. But the entropy and complexity of biological systems is huge and even rodents can outperform state of the art models at general tasks.
IMHO, the quickest path to AGI would be to focus on climate change and making academia more appealing.