Those aren't good interface ideas those are features that alot of trial and error and research went into. Think of it like a new drug. Theres alot of R&D poured into these things. not on the same regulatory or financial scale but work goes into that. Facebook blocks the growth of these by copying wholesale and throwing it at its database of users so they never have to leave their ecosystem.

Look at what instagram has become from photosharing app to an everything platform that has a horrible UX.

> I would be happy about FB dying, but what is wrong with copying good interface ideas?

Nothing, in my opinion. The problem arises when a company is so large that simply implementing a good interface idea completely destroys the value of the original. The best example is Snapchat. Snapchat got big, fast, because its main conceit, while simple, was pretty unique. As soon as Instagram implemented it, Snapchat fell off a cliff, because why use Snapchat when you can just use Instagram?