"Then Facebook announced that for all your best efforts to drive organic engagement, the reality is that only about 15 percent of your content would actually be visible to those people who had specifically requested (through “liking” you) to see your updates."
From the perception of someone saying they "like" something, that (in the origins of Facebook) was exactly that, and not a way to connect to a post stream
So what FB is doing there is preventing a single (tenant) entity from ruining the experience, and this is laudable.
FB don't want to die a death by a thousand cuts (or cat pictures, or 'reshare if you want Jesus in your life', etc, etc)
So if they are showing it by relevance this is important.
Of course the opposite happens as well, like in G+, that is so feud like, only the most popular content ends up there, so you may have the long tail, the most popular content and a gaping hole in the middle