The Gell-Mann Amnesia effect seems to be a specific version of something more general: cognitive dissonance. The fact that the media is not to trust is not forgotten, it is simply not evaluated and acted upon. It sits there in your brain until you sceptically reflect on what you think to know and how you act. Some people do that to some degree, most less so.

We have had a long time to recognize that our brains don't work well. It is time to accept the facts.