There's an interesting book [1] that talks about how media changes over time. In short, new media forms replace older forms, pushing the older forms into niches. An obvious example is TV replacing radio, where radio used to be full of story-based content, but when that content moved to TV, radio became largely a niche form of media, focusing on music (and talk shows and weather etc).

This paints a picture of media forms along some continuum, which describes what you're looking for.

[1] Media Literacy, W. James Potter