I don't think this is true. I was born towards the front end of gen x - 1969 - and I had a vic-20 as a teen. Most of my friends, including some that were definitely not in the "nerd" circles I ran in had them. I had friends with commodore 64s, tandy color computers, timex sinclairs, etc. Our high school had macs and my jr high had TRS-80s.
By 96 I had a packard bell 386sx that came with dos but ran windows. AOL was a thing and it was a very, very different world than dialing up BBSs on my vic-20 as a kid.
I don't know how much I agree with the author's premise, I would need to think on it more. But I think at least from the perspective of people my age - there is definitely a big difference between how we grew up and what was available compared to millenials. I didn't own my first cell phone until after 2000. By the time the first millenials were 10 in 2006, 77% of people in the US had cell phone subscriptions. By the time they were 15 in 2011 it was over 95%.
I think the article's tone is problematic and some of the assertions but I also feel some agreement in terms of how I emotionally viewed technology and the possibilities it brought compared to when I talk to younger people now and how they see it.
The youngest millenials are ~26 years old, born in 1996 according to US census definition. They were already 13 when Whatsapp was invented, much older when it became popular.
Replace Gen X (avg 47 YO) with millenial (avg 33 yo) and millenial with Gen Z (avg 20 yo) and at least the premise of the article starts making more sense.
The average Gen X had no computer in their teens. Millenial had dial-up. Gen Z had iPhones. Who is most likely to care about open internet vs walled gardens?