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.