Comment by macNchz
The most fundamental difference 20 years ago was that online activity was diffused across many different sites, and there was no algorithmic content feed recommending an endless stream of new things. Finding a rabbithole or dark corner required some degree of chance or intentionality, whereas now they are formed around you automatically as one toe in the waters of a given topic prompts the machine to deliver it more frequently and more intensely to keep your attention and draw you deeper in. This is, I think, absolutely foundational to so many sociocultural issues of the present.
I think an even bigger difference is that there was no concept of users monetizing their own usage via advertising or a personal brand. People were in it purely for the love of the game, and maybe some imaginary internet points.
If you wanted to make money you might try hosting a community and monetizing it somehow, but the concept of building a digital following and using it to market products/services (and not be seen as spam or a sellout) simply did not exist.
I recently capitulated and started using real-name HN/reddit accounts because personal branding is not just common now, it's one of the main ways of reaching users.