I've learned information retrieval in university before ever using any full text search engine and I was honestly kinda surprised that most engines are literal textbook implementations. IR was one of those courses where I definitely expected the SotA to be further out than the third slide deck.
That’s probably because SotA in IR is proprietary implementations like Google Search, the most bread-and-butter trade secrets of their business. So they’re not publishing that (at least in any holistic manner, and even if they did, it’s not like one product could implement all its functionality including the complexities around the periphery). And what you’re left with is some pretty decent parity between industry and academic SotA, same as a lot of other areas of CS (databases, decentralized systems, etc). If anything, in most cases, implementation lags behind academic theory.
