"AI is harder than we think" of course depends a bit on who "we" is. The paper seems to focus a bit on the types who thought it's a bit of symbol manipulation you can do in lisp which has always seemed a bit dumb. Then the "it'll never happen" crowd seems dumb as well given people do think and seem to be built from atoms and stuff obeying normal physics. The more sensible view it seems to me is to compare neural comp…
About half of the paper is about modern deep neural networks, but can you please give a few examples of the kind of AI you say is "a bit of symbol manipulation you can do in lisp"? Because I would say this is an extreme oversimplification borne by terminal unfamiliarity with the subject, beyond what may be commented on twitter.
For instance, remember that Deep Blue, despite its name, had nothing to do with deep learning or machine learning of any kind, and was a manually programmed system, yet I doubt anyone would sensibly describe it as "a bit of symbol manipulation you can do in lisp".
But please give examples of what you mean.