It's a problem with evidence based product design. It's in almost all big products nowadays. The way Google axes products, the way Netflix axes series, the way Facebook populates the timeline. They're throwing away the intrinsic value of the product, for positive graphics in their monthly user engagement presentations.
Facebook's user engagement is probably higher than it ever was. I have a friend who's one of those conspiracy nuts and he's on there all day everyday posting dozens of media links to questionable content. His behaviour is their dream. At the same time almost none of my "normal" friends or family are still there. But they never had much engagement anyway even at the peak they maybe checked Facebook once a day for a couple minutes and maybe post something once per month.
Probably these platforms are all approximating the optimal amount of crappiness they need to be maximally profitable.
I've never owned an iPhone, but Apple's approach is the long term one, where they come up with a product that they believe in and they think the customer should use, regardless of whether they actually want. It let's them always carefully control the quality and resists the temptation to make a quick extra buck. In the end it makes them basically unbeatable, where Facebook has to buy competitors to remain relevant.