It depends on the time frame you're looking at. Sure, the very, very beginning was that isolated, but by the mid-to-late 1990s, almost any first-world country resident could get to it if they really wanted to. Varying degrees of how hard you have to "really" want it still, of course. But you certainly had non-trivial "alt.anything.you.can.think.of" communities for LGBT, any radical political position you can name that existed at the time, obscure anime fandoms, or anything else you can think of. The mathematical principle of "regression to the mean" ensures that you get a non-trivial diversity (by pretty much any standard) long before you get to the point that "everybody" can get on there. You do not need access by literally 100% of the possible population before you get "diversity". (After all, the internet is still not there yet either even in 2020.)

(The only exception is if by "diversity" you mean "exact proportionality of representation"... but that's not the same thing. If you want to say that, go ahead. At that point I will agree with you that there wasn't exact proportionality of representation... but then, there isn't today either, nor is it even clear how one would get there, especially as you crank the requisite "exactness" up. Two decimal places? Four?)

Yes, sure, but that's like saying that country clubs are diverse because members have different hobbies. If they really want to, anyone could join, it's just easier for some than for others.

My point is that it's a diversity of opinions (maybe; they tend to be closer together on the important things, too, demographics predict politics fairly well after all) and of hobbies or interests, but not of backgrounds, i.e. where the rubber meets the road. I understand that people usually do not mean "the conservative child of lawyer A and the progressive child of investment banker B chat about their shared interests with the apolitical child of entrepreneur C", but "the child of a lawyer, the child of an office worker chat with the child of a day laborer".

Again, I don't mind it not being or having been like that, I don't see any intrinsic value in diversity by itself. Calling it diverse just sounds like a misrepresentation of what it was.

This sounds remarkably elitist. And honestly if one were to analyze the trolls of the world, I'd wager "upper middle class" (or simply middle class -- it was hardly so exclusive) and "educated" would be a dominant trait.

A single university is an wide spectrum of participants. Yes, there are some demographic commonalities, but there are so many significant differences. Now add universities across the spectrum and across the globe.

> A single university is an wide spectrum of participants.

Is it? Sure, you'll have people studying physics, law and economics, but they'll be pretty similar in background. I'm not saying that usenet was a hive mind, far from it, but it certainly wasn't very "diverse" with regards to the background of participants.