If you count game demos on the web, then Epic Citadel, based on the port of Unreal Engine to various mobile and web platforms including HTML5/WebGL/asm.js, had a much detailed and more 3D world - it used all 3 dimensions fully, unlike OP which appears to be a flat world that’s quite restricted vertically. That demo first came out about 15 years ago, with the HTML5 version coming out a few years later.
Since then I’ve seen several other sites along similar lines, since Unity released a similar capability, but I haven’t kept track of them. The problem is they’re all essentially games that are more impressive for their look than their functionality, so they tend to have a spike of interest when people first see them and then you never hear of them again. And typically, the tech bitrots and the sites stop working after a while.
How many cooler 3D websites do you know? I personally know less than 10, and only https://messenger.abeto.co/ off the top of my head.