As someone who is currently working on successful commercial product with a strong a expert system component, I agree with the sentiment. The funny thing about this project is that the product owners nor marketers and not even the coders ever use the term "expert system". It just doesn't sell any licenses nor garner any attention.
My view is that expert systems are a ubiquitous part of many products to the degree it's hard to even recognize them as such. They're not the main focus of anyone's marketing budget, because that makes about as much sense as promoting your "revolutionary axle technology" to sell a car.