Earlier quoted context omitted.
>20-25 years ago when there were half a dozen prominent engines That's not how I remember it. My recollection is that for a year or 2 (roughly 1998 and 1999) Altavista was the dominant engine, which rapidly gave way to Google essentially as soon as Google became available, and since 2000 Google has been the dominant engine. In the late 1990s and early 2000s, I was getting my info on what engines people were using mos…
Alltheweb was fairly prominent then. The likes of Ask Jeeves and Lycos had a few % market share. Gigablast also had its day back then.
During those years, I also used DMOZ regularly, which is not a search engine, but rather an index of links organized much like a card catalog in a library is.