My guess is that the advertising industry has stratified and now the advertisers are rarely self-producing content. Now they just buy stock footage from content

My guess is that the advertising industry has stratified and now the advertisers are rarely self-producing content. Now they just buy stock footage from content producers and add narration, text, music, done. All of these can be sourced from marketplaces and put together cheaply, a consistent process making for a steady stream of content with varying degrees of blandness.