... since they did not appear to stray far off historical facts, this story sort of wrote itself.
Good movie, good message, lots of good efforts, "needed to be done at some point", but somehow left me feeling I had just done an assignment in civics class. (Maybe that was the whole point).
WARNING!
Objects under T-shirt are larger than they appear!
You are right to a degree. But the writers still had to decide which parts of the story to put on film, how to sequence the parts, where to start and where to end the movie, and what peripheral characters to add. Not to mention the creative license that the authors took. Did Murrow really have that conversation about censorship with CBS brass? Perhaps, but if so, I doubt that it was recorded for posterity.
GNGL would have easily been a much different picture has Clooney chosen not to start and end the movie at Murrow's award dinner/speech about television.
I also see your point. After falling in love with this film, I realised that it was pretty much a dramatised documentary. However, the dramatic arc wouldn't exist if it were an actual documentary. By making a regular narrative feature, Clooney makes us sympathise with Murrow et al, which makes it much more interesting than an orthodox doco.
There is also another agenda created by the framing speech at the TV awards, which pops up in the Liberace speech: that television has a duty to inform its viewers, rather than feed us rubbish all the time, which it is increasingly doing.
We're all in it together.