It's a common thing to hear these days, about how horrible everyone is on the internet and that no one is nice to each other. Did people have these attitudes at the turn of the millenium? Or is this a more recent phenomenon due to social media (out of the scope of the sub I realise) ?
It's hard to answer this because the internet is a big place, so this is a rather broad question, big enough that it's hard to make any conclusive statement about its general 'attitude'; this is as true as it is now as it was 20+ years ago. On the other hand, the nice thing about a question like this is that we can - after a fashion - go back to the 1990s and look at what people said then. For better or for worse, the observation that the internet never forgets is not entirely untrue.
I will draw on the discourse on two platforms here, IRC and Usenet. There were other platforms - the 1990s saw the rise of instant messengers like ICQ, for example, as well as the founding of what we would now call social network sites, such as SixDegrees. But IRC and Usenet are the platforms I have studied. In terms of activity, the heyday of both of these platforms is arguably around the turn of the century, but they go back to 1979 (Usenet) and 1989 (IRC), so they are excellent sources if one wants to study what the attitude of people on the internet was before the rise of what is often referred to as 'web 2.0', which is usually understood to include social media sites that are now under increased scrutiny for issues such as algorithmic bias, online bullying and spreading misinformation.
Before we get to the part where I discuss what people on these platforms thought about the internet, let me briefly introduce them. IRC is a chat network, or more accurately a chat technology; there were multiple IRC networks, and on a given network you could find numerous channels dedicated to a specific topic. If you've used Slack, you know the model; Slack's convention of prefixing a channel with a '#' is taken directly from IRC. Discord is also comparable. But most IRC servers were far bigger than Slack servers, numbering in the 100,000s of simultaneously connected users during its heyday, talking about an extremely wide array of topics.
Usenet, then, is a loosely decentralised network of discussion groups (called 'newsgroups' for historical reasons), organised in a hierarchy. There are a couple of top level categories, and within these one could create groups at any depth of subcategories, though usually three or four levels deep was the maximum. So you could talk about conspiracy theories related to Princess Diana's death in alt.conspiracy.princess-diana, but there were other conspiracy theory groups in the alt.conspiracy hierarchy; or you could find people to talk to about exploring your sexuality in soc.motss; or you could talk about IRC (to make things a little meta) in alt.irc.
All this to say that if you are looking for the thoughts of online people on a specific topic in the 1980s-1990s, there is a good chance you can find a Usenet group or IRC channel that covers that specific topic. There are a couple of Usenet archives that are relatively complete for this era. IRC chat logs are harder to come by, and more fragmentary, but they do exist. I will mostly refrain from citing messages or groups directly here though, because the internet was a far smaller and less anonymous place back then and people do not necessarily appreciate their messages from 30 years ago being recycled, now that everyone is online and putting your home address or phone number in your signature (as many people did back then) can be a real danger. But if one were to go look for conversations people had at the time, this is where one might look.
So, if you browses these archives, looking for opinions about the internet, what do you find? I think the best way to summarise this is a mix of utopianism and cynicism. Especially around the early 1990s, countries were still slowly being connected to the internet one by one, and internet connections were quite sparse anyway, so there was a steady stream of wide-eyed newcomers experiencing the internet for the first time and being thrilled at how easy it suddenly was to talk to likeminded people, sometimes from the other side of the world! Even the people who had been on the internet for a while were often still quite hopeful for the way it could maybe change the world for the better. The best example of this is the manifesto 'A Declaration of the Independence of Cyberspace' by John Perry Barlow from 1996. It is quite representative of what the more idealistic users of IRC and Usenet might say. The manifesto shows an idea of a 'cyberspace' separate from the laws and conventions of the real world that many would call hopelessly naive nowadays, but there was still a strong idea of the online being somehow separate from the offline, and a 'blank slate' to some extent, so it was easy to project all kinds of (utopian) ideas on that basic notion.
To be sure, this is an extreme (though influential!) example; most people were more level-headed than this. But there was still the expectation that access to online conversation would allow people to share experiences with like-minded people more easily and also enjoy a degree of freedom to for example experiment with their identity outside of the social conventions that they would have to deal with offline. This would then perhaps change the world for the better.
And, on a very basic level, if you were a Finnish teenager it was super mega cool to suddenly be able to talk to someone in Japan! This notion of "real-time interactive communication in a convenient, cheap manner with people from around the globe" (as someone put it at the time) was still novel for many people and they were quick to ascribe all kinds of lofty expectations to it, even though it may seem mundane to us now (just go to /r/japanlife or something, right?). But, this being a new experience, there was a tendency to focus on the positive. Incidentally this pattern can be seen in the early years of virtually any communication technology; when the telegraph was invented, people expressed the expectation that now people could send messages to each other in real-time, war would be a thing of the past (we all know how that went...).
So in those days, there certainly was a sort of naive optimism that you don't really see anymore, if only because we now take for granted what seemed new and exciting back then. Nevertheless, not everyone was wearing rose-tinted glasses. While comparatively a lot smaller than it is today, the internet had existed (in one way or another) for about two decades already in the 1990s, so there had been plenty of time for people who had been around for a bit longer to either abuse it or become disillusioned with it. IRC particularly was rife with horny teenagers (?) which annoyed many, see e.g. this satirical "guide to Net-Sex"; neo-nazis were publishing guides on how to infiltrate other Usenet groups and recruit people (and a common counter-tactic was to spam the hell out of neo-nazi Usenet groups); queer-friendly IRC channels were victims of frequent 'drive-by' spam, where people would join and spam queer-phobic expletives until they got banned. In fact these 'IRC wars' between channels were a big problem back then and incidentally an early driver for the development of automated moderation tools, but I digress.
The big difference here is scale. More abstract concerns about filter bubbles, or algorithmic bias, insofar as those were even considered at all, were less pressing because in the absence of the internet's modern ubiquity, it has far less of an agenda-setting power; even if a platform was problematic in one way or the other it would influence only a comparatively minuscule amount of people. Arguably, cynical attitudes towards the internet were more focused on describing the internet as a failure of sorts, because it was full of nazis/porn/horny boys pretending to be girls/bigots/et cetera. It is in fact full of all those things, of course, but the cynical attitude was that this was all that it was.
So, in summary, insofar as it is possible to answer a question as broad as this one, I would say that pre-2000s, there was an idealism on and about the internet that does not really exist in the same form anymore today. But at the same time, people will be people. As such, there are plenty of examples of problems similar to the ones we have today, and of people being horrible to each other, and of others being annoyed at people being horrible to each other. But all of this at a smaller scale.
If you are interested in this sort of thing, I can recommend sources written at the time - these are a couple I have used in my own research that are quite emblematic of how the internet was viewed during the 1990s (though they were all written by Anglophones and as such, like my own post here, they are focused on a particular part of the internet):