"The height of the dot-com era" was 18 years ago, Linux has come on a long way since then - not to mention the (perceived?) quality of Windows and macOS going downhill.
Even fewer people in my extended group of friends and family are aware of Linux now than 18 years ago, and that is saying something. The only people who know anything about it are geeks, and we are a minuscule amount of the population.
I think fewer people are aware of underlying software generally. Presumably there are at most four categories for lots of end-users: "PCs", "Apples/Macs", "iPhones", "Androids". (Of course, more people are using Linux in some form or other now than they were 18 years ago, whether they know it or not.)
For one thing there are a lot more distros, two different display servers, and several more packaging formats. Not exactly countering their point about fragmentation are we? At least we got that sound situation mostly sorted out.