The modem itself is certainly interesting but the author's tone is very condescending. Who is Hackaday's target audience, anyway?
He's talking about VERY old technology. The older the tech is (and the more obsolete), the more likely it is that younger people won't even know what it is when they see it. That's not a strike against them, it's just a product of the rarity of the item in modern society.
"Fortnite is most popular among players between the ages of 18 – 24, who account for 63% of all Fortnite players." ( https://www.vertoanalytics.com/chart-week-deep-dive-fortnite... ). So the author is saying -- if you play Fortnite, you are likely to be fairly young, and if you are fairly young, there's a good chance you don't know what an acoustically coupled modem is.
I think that's a reasonable thing to say. Perhaps when I have time to finish the article I'll see something that changes my mind, but at this point I think it is worth giving the author the benefit of the doubt.
It set the tone that you read in your head, but the rest of the article is fine (and really interesting!) if you can ignore that first paragraph and read it in a neutral tone.
(NB: some voluntary sarcasm has been inserted above)
"Very condescending" is a stretch. The most suspect thing I could find was the "fortnite" comment. It's a throwaway joke that won't amuse everyone.