Indeed - this is often forgotten but just like the fashion of necktie widths and the length of hemlines, so the AI pendulum swings from symbolic representation to ML. I believe it will return, eventually, and at it's foundation rests LISP or at least the core tenets.

Prof. Rodney Brooks (MIT, Robot Lab), who is famous for his subsumption architecture (SA) and against Minsky's central-model of representation (arguing instead for radically separate distributed systems), wrote SA and nearly all of his research in LISP. In fact, Brooks wrote a book on LISP programming and developed his own efficient LISP engine. Many, many of his grad students have gone on to become leaders of the AI (not ML) world.

Curiously, I am now reading "The Elements of Artificial Intelligence - An Introduction Using LISP" which depicts a "Knowledge Engineer" which stirring a cauldron labelled "Expert System". Copyright is 1987. It's a joy to see how far we've come in some respects, but how little progress in others. Perhaps this represents a measure of the maturity of certain subdomains?

I suspect in another decade "we" will rediscover the wisdom of those who have developed symbolic knowledge representation.