Depends about on what you mean here. The good scientist mostly give up when trying to 'describe' higher level function (at best maybe generate some analytical expression which may correlate with IQ or something) and focus instead on biochemistry at the single neuron level. That's a very different science than trying to 'explain AI'.
Have we made any fundamental progress in understanding how the human brain works in the last 20 years? 50?
Issue there is the ability to trace out the brain networks accurately. We're getting closer. Once we're in the ~0.5 micron scanning range, things will get VERY interesting.
I believe we've already mapped some invertebrate brain, maybe 250 neurons.
We've made pretty good progress. But the same problem that plagues explainabilty of ANN's rears its ugly head in neuroscience.
Low level descriptions provide shockingly little insight into high level behavior.
Yes, but also your original question was about how much people care, so questioning the amount of progress is at best a weird tangent.
I am genuinely curious. It doesn't seem like we have made the slightest progress in truly explaining how the human brain works or why we are sentient and self-aware.