HN doesn't do much, but Wikipedia does a decent amount of stuff with JS on their website despite people taking it as an example of "the web as documents"

meanwhile, I don't know how FB or Twitter are nice user experiences when you operate on a "paginate 20 tweets at a time" philosophy.

I don't think it's either/or. You can make a "flashy" (in the sense of Buzzfeed) without it being burdened by huge amounts of js. Likewise, monetized sites are still frequently not like Wikipedia or HN.