Set theory is fantastically interesting and powerful, but it's very very understandable to brush past it so we can get to the pretty pictures.
Also, if I do actually "take 3 seconds and search 'introduction to set theory'" I find two (excellent)[0] resources that, in their introductory paragraphs alone, rival the largest sections of the original link.
" Outside the scope of this textbook".
The similar phrase, frequent in textbooks:
" Proof left as an exercise to the reader"
was no less annoying. But you can't cover everything and given that sets aren't important to this post, indeed covering them would be more confusing since the Javascript Set.prototype has things such as being finite, and strict equality.
This article is not an introduction to the mandelbrot set, it's "how to draw the mandelbrot set in javascript". I read this as a programming blog post not a mathematics blog post and enjoyed it.
I live overseas and have no reason to talk to kids so I'm totally out of touch with the "real Millenial generation". But I want to know how they talk and think about things. I tried "Millenials react to X" videos but nothing is that useful.
I don't think it's very good if I'm totally out of touch or don't understand the Millenial generation at all. For me ( 80s so that's a gen-x-er? ) Millenials really seem like an important generation to understand...they grew up with the internet. They act differently online to the rest of us ( more privacy conscious and so on ). It's frustrating that I can't find any first-hand sources or interviews to see how they think and talk -- except things that are parody / making fun of it...or just theorizing by "experts".
The other side of this is about inspiration. I realized that as I got older, my "generational culture" ( for want of a better word ) is basically static. The shows, the movies, the music, the people, the scene, the lifepaths, opinions and ideas of peers...it's all just...so familiar. So boringly familiar. And unchanging.
Only the new generations can really have some vibrance, vitality and fresh inspiration, in a very organic sense, in my opinion. Not just fresh relative to another, static generational culture, but somehow inherently fresh and inspiring. It really makes me appreciate youth in a way I didn't before. As, if nothing else, this source of a fresh way of looking at the world. I also think that youth who grew up in the last 17 years, have to be some of the most interesting, or somehow express the most faithful reflections our world right now -- because they were literally shaped by all the huge changes that Earth has gone through -- Western political changes, rise of China, terrorism, social media. So I think to some extent if people want to understand the world we live in now, we have to understand the generation that grew up shaped by it.
The text certainly didn't inspire me to enable JS so I could see the code or images.
I think it's a shame we seem to be veering ever more toward 'code is all that matters' (or whatever the product of work is if not code) - not writing, presentation, communication, etc. - the result is rampant unprofessionalism.
"...but maybe it's worth a mention?" I don't know, is literally one of the fundamental parts of the underlying mathematics important? "...Wonder what would be a really good succinct but not wrong explanation of set theory…" Here's an idea, take literally 3 seconds, or the minimal amount of effort you have and search 'introduction to set theory'. I can almost guarantee that there is a plethora of fantastic resources out there. Hell, Wikipedia is often more than adequate for mathematics topics. Also, unless you're a James Joyce tier writer, this stream of consciousness style writing is exceedingly poor form and should be avoided. It adds nothing and really only serves to tell the reader how little you know.