@Olivier5,
As you note up front, the WP accepted vanden Heuvel's piece for publication.
Beyond that, I don't think there is anything in the piece, from either Sanders or the author, with which i have any serious disagreement. The critique she and Bernie make are the same critique that Chomsky has been making for years - that major cultural media tend to support the status quo. It is a critique I agree with.
But similar critiques can be made about, for example, the major religions in a culture. American evangelism is a poignant contemporary example. Why? That's probably pretty damned complicated but one key factor is just that it is usually easier to go with the tide rather than against it. Consensus and agreement, broadly spread across a culture or community, is necessarily a key component in that culture's or community's cooperative functioning and continuance. And yeah, there is both good and bad in this.
These dynamics exist outside of and previous to the modern corporate world. But that world will respond similarly. Which is why I am all-together in favor of strong regulations limiting corporate ownership of media and of limiting any news entity from overwhelming penetration in any region.
As to the "entertainment" factor - god help us but I don't see how that changes. That is a response to consumer demands and to human nature.