I mean, WebGL was released in 2011, so this kind of thing was possible for like 13 years. If you go back once again as much, to 1998, the web has barely existed back then.

There were things, like Epic Citadel, a full port of Unreal Engine to the browser (using asm.js, a technique of compiling assembly to Javascript) a decade ago:

https://www.youtube.com/watch?v=l9KRBuVBjVo

And yeah even that somehow feels futuristic today.