The six they list doesn't include YouTube, Facebook, Instagram, TikTok etc where a huge amount of media is consumed.
And would they count YouTube as "one" outlet? I would argue I have greater choice of amongst YouTube creators than I ever did compared to, say ABC, in 1983.
The analysis also seems flawed in that they evaluate movies based on box office sales. Which excludes giants like Netflix?
There may be issues here, but this article wasn't very good.