I believe your are using popularity as a metric of quality which is not always a safe assumption. It’s like saying that Taylor Swift’s music is better simply because her albums sell lot more copies than others. The fact that billions use Facebook or Craig’s list doesn’t mean that they love the interface or that they wouldn’t prefer a simpler one or that is the best possible design.
A simpler design is not by definition better. That is why Dieter Rams’ principle is “Less but better” and Johny Ive believes that “Simplicity is not the absence of clutter; that’s a consequence of simplicity. Simplicity is somehow essentially describing the purpose and place of an object and product. The absence of clutter is just a clutter-free product. That’s not simple.” (emphasis mine). The designs you are referring to in this article are not simple, they just failed attempts to achieve a design that is less cluttered and at the same time better in terms of functionality, usability scalability, performance and many more.
True simplicity is really hard and requires tremendous amount of work and time to achieve. This is the true reason why we still have cluttered interfaces like Facebook’s or Photoshop’s. It’s really hard to make them simpler but that doesn’t make them good or a proof that we don’t need a radically simpler design.