All those news sources have come to depend on Google. They hate it, but they can't fight it. News revenue is way down in this Google world, with viewers passing by whenever Google deems it best.
Any news source that opposes Google is at risk of getting blacklisted and they know it. You might find a bit of coverage on sites that are already blacklisted, like Breitbart. Nobody else would dare anger Google.
I'm sure that most news sources would love to see Google get hurt, but going after Google is like going after the king: you'd better not miss.
That could explain a part, but not the entire phenomenon.
Fear is a negative emotion, but is quite visible to those who are under it, and they would try to get rid of it.
But the journalists (ok, let's them call so for now) do not seem to be driven by fear. The media owners might be, but the journalists aren't. They have a positive emotion, they want to do thing the way are being done; they seem to be driven by shared ideology of progressive liberalism (see twitter for blue checkmark social bubble). They believe they are doing the right thing, even if it means being silent about some wrongdoing. The end justifies the means, and talking about some issues would be like helping to the enemy. Nobody wants Trump in 2020 again, right?
That's why you are seeing dissent only in media, that are not progressive. And they happen to fall outside main media sources by definition.