The peak of TV watching was actually around 2010, it's gone down since then (although still above 1996 levels!) -- replaced of course with internet use of various kinds, including kinds that could be considered "fiction consumption" as well as not (social media I would only consider fiction consumption as a joke!).
Another thing that has gone down since 1996 is leisure reading time (again they don't usually count social media as leisure reading though).
I don't have numbers on how much time a medievel European peasant spent listening to stories, plays, or narrative music.
People may have on average more leisure time than they had 500+ years ago! As you say, "The luxury of doing that en masse simply was not possible." But now we're talking about a different thing, the OP's claim was that "we invest so much time and energy into fiction, far more than did any of our ancestors" because of a crisis of moral shared meaning, not simply because of an increase of leisure time.
The leisure time of people in different social positions in different times and places is another (interesting) question, but I think people have always chosen to use much of their leisure time (time not required for material survival) and energy on fiction.
The TV dinner was popular over 50 years ago -- people didn't have time to actually eat without consuming fiction
Handwringing over "time wasting" activities is as old as time, whether it's video games, TV, newspapers/radio or gambling, drinking and dicing.
Of course it is obvious. People waste their lives away consuming fiction in the way of books, netflix, video games, politics. The luxury of doing that en masse simply was not possible if we go ways back. Hell, just in my lifetime this has changed. 25 years ago I heard of no one watching ten episodes of a series in one sitting.
I believe most people now spend far more time with and engaged in fictions than reality. People even think that the fictions media create are real. Most news are editorialized and fictionalized. What is presented is not reality. What people spend most of their time on a phone on, social media, are to a high degree fiction. That is not reality you are engaging with.
Reality is closer to the bottom of Maslow’s pyramid than the top.