> 4chan's design is early web 2.0, doesn't require you create an account, allows (pseudo) anonymous posting, content is mostly unfiltered, unmonetized, free & thought of as ephemeral, etc.

That is hardly unique. There are any number of phpbb (and other) boards that allow mostly the same that were/are/will continue to be the same. The only difference is the clientele and noteriaty, but I'd argue 4chan is basically the same thing as somethingawful is/was in that regard. People act like 4chan was this ground-breaking thing but it was just one of many many similar boards.

Also for 4chan, you'd only go to 4chan to go to 4chan. People went to geocities and xoom and angelfire and all the other old internet things for niche website content from individuals, not because of the site that hosted it. It's like going to a bar to chat vs going to a library to study: going to the bar/4chan is an undeniable part of the culture, but let's not pretend it is anything significantly different amongst a constellation of other chat/forum sites (somethingawful, fark, ebaumsworld, discord, IRC etc etc etc)