And are you using relative or absolute popularity? E.g. "medium form" articles in pop magazines were probably always more popular than longform ones in literary mags, but were they more relatively popular than "tweets" or "tiktok videos"?
Would a three hour film like Doctor Zhivago ever sell 248 million tickets today? And that number has a lower total population size to pull from! For a focused experience without your phone, or work, or anything else (compared to listening to a podcast in the background while working or driving)?
There are groups that still enjoy, or are learning to enjoy, longer stuff still. But that's not the dominant trend.