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?)
