The average person has no idea what 90% of the headlines on HN are even referring to, giving it a degree of self-moderation.
Twitter, Facebook, etc - everyone knows them.
Reddit, Discord
HN, presumably other domain-specific forums, IRC
Fediverse (though less so as of late), lobste.rs, presumably many that I don't know about!
Taking the larger number of people outside of the US that only use mobile devices and only use apps like FB, WhatsApp, or others I'm not familiar with, I'd go so far as saying that the average person doesn't know websites exist. If it's not present to them via an app, could they find an actual website (or at least would they even attempt to)?