Tumblr (assuming it survives as it exists now) fills the niche that geocities once did, except it slaps a nice UI on making updates and presents some minor restrictions on what you can do (you need to find somewhere to put some of your assets that can't really be hosted by tumblr themselves). Their theme editor even has (if my memory does not trick me, I'm at work and don't particularly want to log into my tumblr dashboard) a reasonable HTML editor. If all the eye melting gif backgrounds, autoplay music and late-90s knock off novelty cursors are anything to go by, a lot of tumblr is probably a more worthy descendant of geocities.

There is certainly a shitton of content created on tumblr, even if you discount the value from aggregation. In addition, Neocities 10mb limitation hugely limits what you can do. Setting aside 1MB for CSS, JS and images and assuming you have a 85/15 content/markup split in your files, you get ~150k words. If you even dare adding images, the possibilities for archiving any content you produce are shot.