Is the expert system still in use today?

It's correct that knowledge based Expert systems have fallen out of fashion. They were intensive researched in the 1970s and 1980s. The new, more exciting topic, is called data-driven and machine learning approach. This kind of turnaround can be traced back in the literature. Since the 1990s lots of papers were created about data-mining and only a few literature was written about classical handcrafted expert systems.