Expert systems were a “flop” only in the sense that they were so apparently promising early on (like in the same early phase as we are in now with transformer architectures/LLMs) that people projected, well, the same kind of universal and unlimited capabilities now being proejected for technologies based around transformers, so lots of projects in virtually every domain were undertaken with wild expectations. It turns out that expert systems were
wildly successful in terms of what they were useful for, but even so, but, even so,
lots of those efforts failed because the expectations were so ludicrously high.
> In fact, a good portion of the automation systems in the facilities are more than 30 years old.
Not sure what you are trying to say with that, given that the expert system hype wave started about 60 years ago and and petered out between 50-40 years ago.
The rule-based systems resurrection ~25 years ago (while seeing a much wider array of practical applications developed) had much more modest expectations, and though it was centered around expert systems as the enabling central component of broader systems, almost never used the term “expert systems”.(Though I wonder if you are thinking more about fuzzy logic, because while it wouldn’t be significant for unqualified “expert systems” as such, the timing would kind of make sense for saying something about fuzzy logic systems, whether fuzzy expert systems or neurofuzzy systems, both of which had a bit of hype cycle starting in the mid-80s which, IIRC, saw lots of attempts at industrial applications with mixed success in the 1990s.)