It’s probably just a definition thing.

To me, constructive criticism means that the criticism doesn’t just point out failure, but that it then also shows how to correct that failure.

By itself, “you’re doing it wrong” is just destructive: it takes something apart, it destroys it. Without a subsequent “and here’s how you would do it right,” it doesn’t become constructive, it doesn’t help in putting things back together in the correct way.

Sure, as a first step, “you’re doing it wrong” is completely justified when something is actually wrong.

But without the second step - the constructive part - it just doesn’t constitute constructive criticism. By itself, it’s just criticism.

Is saying “you’re doing it wrong” really constructive?

Yup.

Facebook has been around for almost two decades.

This is not some unknown guy - we know exactly what Facebook’s business strategy and ethical and moral conduct looks like.