I have always thought of Cyc as being the AI equivalent of Russell and Whitehead's Principia--something that is technically ambitious and interesting in its own right, but ultimately just the wrong approach that will never really work well on a standalone basis, no matter how long you work on it or keep adding more and more rules. That being said, I do think it could prove to be useful for testing and teaching neural net models.

In any case, at the time Lenat starting working on Cyc, we didn't really have the compute required to do NN models at the level where they start exhibiting what most would call "common sense reasoning," so it makes total sense why he started out on that path. RIP.