Agree completely. The brain is so incredibly complex that we've barely scratched the surface. It's not just neurons, which are very complex and vary wildly in genetics between them - it's hundreds of other helper cells all interacting with each other in sometimes bizarre ways.
To try to boil down it all to any simple signal is just never going to work. If we want to map consciousness it's going to be as complex as simulating it ourselves, creating something as dense and detailed as a real brain.
I don't think it's anything other than electric activity, but it's clearly not "some electrical signal". It's the totality of them. They are many, and complicated. And they seem to be required for consciousness. Doubt there's any proven conscious state in a human, lacking electrical activity in the brain.
Re just electrical activity, I think you can add empirical evidence it's chemical as well as beer and other substances can affect your perception of reality.
To try to boil down it all to any simple signal is just never going to work. If we want to map consciousness it's going to be as complex as simulating it ourselves, creating something as dense and detailed as a real brain.