While a lot of the content was junk, GeoCities is an important piece of web history and it's sad that Yahoo will not keep the content online. Fortunately, some sites like Archive.org tried to salvage GeoCities but we're afraid that some information may be lost forever.
Here's a bit of GeoCities history from Bright Side of News:
The company started in 1994 as a small ISP dubbed Beverly Hills Internet by David Bohnett and John Rezner. Meanwhile, David turned into a philanthropist and an investor in promising internet startups. Back at the day, free internet hosting was something you could only dream off, and GeoCities offered 6MB of webspace, considered "infinite storage back then". GeoCities divided interests into "cities", such as "Hollywood", "SiliconValley", "New York" and so on.
Sites such as AnandTech started its existence there, before turning into multi-million visitor portals… but unfortunately, that was not the destiny for GeoCities. Acquired by Yahoo in 1999, it looked like neither Yahoo nor GeoCities have the idea how to develop the hosting service.