So my point remains. I'm not saying there's nothing to learn. I'm saying that we cannot go deep. That we currently cannot understand the brain to the degree we understand other systems. And that there are fundamental difficulties because we're dealing with living beings.
Example papers:
https://pubmed.ncbi.nlm.nih.gov/25391792/ -- "Two-photon excitation microscopy and its applications in neuroscience"
https://www.nature.com/articles/s41598-018-26326-3 -- "Three dimensional two-photon brain imaging in freely moving mice using a miniature fiber coupled microscope with active axial-scanning"
Sure, it's localized and you cannot go deep, but there is so much to learn that that is plenty at this point.