Some of these ideas live on in Neocities: https://neocities.org/

Just HTML and your own assets. No node.js hosting, no JSON+XML backend storage (that we can see), no sweat.

Granted, Neocities isn't built on 1999-era technology either, but I think it better captures the aesthetic of "web sandbox that i get to play with in my own webspace" a bit closer than this.