You seem to confuse observing that a phenomena happens with understanding it.
A good friend of mine from college is an anethestist and we've had long conversations about this and he says that consensus is that nobody knows how their drugs work. They just have extensive history with the "dials" they use so to speak.
I'm not saying that the existence of anesthetic technology means we understand consciousness. That's obviously not the case. I'm just pointing out that what the OP listed as the limiting factor on our understanding is already in hand.
Being able to turn off consciousness in a gross way is in no way equivalent to being able to prove that its origin is chemical.
A complete chemical theory of consciousness would need to explain not just how general anaesthetics work - a field which is much less comprehensive than most people realise - but also how exactly LSD, psiloscybin, DMT, and other hallucinogens produce all the very specific and very different effects they do.
A good friend of mine from college is an anethestist and we've had long conversations about this and he says that consensus is that nobody knows how their drugs work. They just have extensive history with the "dials" they use so to speak.