I can’t think of any field of research where the model used is completely accurate. At one point we will have to leave behind the messy real world. While a simple weighted node is insufficient for modeling a neuron, there are more complex models that are still orders of magnitudes less complex than simulating every single interaction between the I don’t know how many moles of molecule (which we can’t even do as far as I know, not even on a few molecule basis, let alone at such a huge volume).

But I feel I may be misrepresenting your point now. To answer your question, maybe a sufficient model (sufficient to be able to reproduce some core functionality of the brain, eg. make memories) would be one that incorporates a weight for each sort of signal (neurotransmitter) it can process, complete with a fatigue model per signal type, as well as we can perhaps add the notable major interactions between pathways (eg. activation of one temporarily decreasing the weight of another, but in a way bias is sorta this in the very basic NNs). But to be honest, such a construction would be valuable even with arbitrary types of signals, no need to model it exactly based on existing neurotransmitters. I think most properties interesting from a GAI perspective are emerging ones, and whether dopamine does this and that is an implementation detail of human brains.