It’s definitely not dead. Some great demos have been released in recent years in JavaScript / WebGL, e.g. using visual tools like cables.
https://cables.gl/
The Wikipedia entry on demoscene seems to specify that it's about impressive demos on old computers.
Where does it specify that? (and if it did, it would be wrong)
There's a reason why you've got the 4Kb, 64Kb competitions. We want limitations because overcoming them is part of the art.
Lastly I made an Apple ][ demo. I could have learned the shader stuff, load tons of geometry, etc. But I much prefer limitations because I know my peers will check my code and hopefully will be astonished by what I do. (yeah, gratification !!!)