(Btw, the best way to prove me wrong is to write a 64k intro about it)
The source code of all my 64k intros has been shared (the last one was added two weeks ago): https://github.com/ctrl-alt-test/demo-archive/ and my plan is to share more code to help people get started. Creating demos using procedural generation is incredibly fun.
Also back in the mid 1990s maybe the demoscene _was_ instant gratification to get started? You could start doing graphics with "mov eax,13h / int 10 / mov ax,a0000h / mov es,ax / mov di,0 / (loop with stosb).. ".
To get started today with graphics you either setup openGL/d3d with their weird API's with decades of legacy, use something third party (and learn linking/libraries) or write a 3000 LoC hello-vulkan (Or use Unity,etc but then up until 5 years ago you'd get shouted out of the scene due to elitistic attitudes).
I know I can't make anything that competes with .the .product or Chaos Theory (at least not yet), but it just feels like a good limit. 64k is plenty of room for code as long as you don't write a huge amount. You can write all sorts of procedural generation; you can use OpenGL and C++; you can compress it generically with xz (at least on Linux) without worrying about ultimate size efficiency. But it's still small enough that you can't include raw texture or sound data - you're forced to generate them with code. It's still code-based art, not "download a bunch of assets from the internet"-based art that might as well be a video file. A lot of >64k demos spend a lot of the size on content files, which doesn't feel like what a demo should be.
To write a 4k you have to actually make it small, but to write a 64k you just have to not make it big.
Making them is for most more about reaching the upper limit in size and then tweaking until you're happy (more experienced people might have an budget idea from the get-go and might overshoot slightly with their idea and then cut).
64kb can (and often did in the 90s before Jizz and Stash, fr-08 was mostly an well produced evolution) include raw images,textures and samples, and raw data can still be an viable escape hatch today. The killer for 64kb is that you can spend almost infinite time on writing generators and other tools.
Is that even a demo? I suppose. The EXE file seems custom made for this. It doesn't feel like a demo, though. It just feels like they made a music video in some tool like Blender with no constraints, and writing their own playback tool doesn't "really" make that into a demo.
By contrast, anything you can do in 64k that looks demoey is demoey.
The winning entry, "Rainmaker" by "Byte[censored] & Doomsday" was 450 megabytes. 2 different versions are included in the download, making it 900 megabytes, but that doesn't count. It's packed in one EXE, without as easy visibility as the other one which had all its resources in separate files. Running 'strings' shows fragments of RDF, JavaScript. It's made with some tool called "Notch" and the 'strings' output makes me think it might have a whole web browser in it as well as a whole copy of Notch. It also happens to be a valid zip file, where we can see there's an 80MB WAV file of music, and at least a hundred megabytes of textures and objects.
My first demo had a music wave file. That's because I ran out of time and couldn't replicate the way I'd made it in the DAW program. That was a noob thing to do. But the #1 winner at Revision has the same thing? What is this? I don't like it. Demo-making isn't supposed to be about shipping an mp4 video alongside an mp4 file.
My reference on non-generated is that what is nowadays called chip musicians used to do 10-40kb mod's with regular tracker tools that would easily be compressed with an exe-packer to work out of the box for a 64k, logotypes,etc were commonly just palettized images (wasn't much of an issue for mode13 graphics and even early hi-color things).
But more than anything, the top-2 64k's (And some oldschool prods) at Revision probably were the ones with most experienced man-hours put into them.
As for Notch, it's basically the commercialized version of the Fairlight demotools. Also appending Zip's to .exe files is one of the oldest tricks in the book to package datafiles "nicely", works well since the central directory of a zip file is found from the end of a file and you can compile the exe separately and then just insert data-files by making a zip and appending it.
It'd be easy to write an essay on it, but pirates games and cracktros not being as visible in the days of cheap games, copy/lan parties as focal points of computer usage in the 80s/90s, lan party consolidation and separation of demoscene from lan parties, _lack_ of funding for commercial graphics programming (games) before y2k in Scandinavia compared to available talent, inflexibility of early 3d accelerators were all factors in making the demoscene a thing and later it's decline.