no one really went anywhere with it

Sure they did. The connections just aren’t obvious.

Minsky’s research on information classification and neural networks (among other things) are essential to modern machine learning and neural network training, which are used in handwriting recognition, facial recognition, and your phone telling you where to hide a body.

It didn’t turn into Strong AI (yet?) like he hoped, but it’s still been invaluable, and enabled some very powerful human-computer interfaces.

With regard to his classifications of the human brain, I’m more inclined to think they’re not wrong, just not practical to program manually. They’re much more complex than we thought. Which is why we're turning to things like machine learning.

But his classifications still make sense for the most part, I think. We do know regions of the brain are associated with specific functions.

Grand theories sketched out in advance do more harm than good

Darwin? Freud? Einstein? They were all wrong on countless points. But their grand theories created and advanced their fields. 'Grand theories' give science targets. Proving something wrong is just as good as proving something right.