Also a big part of the problem is that serialized narratives are hard to follow when there are long gaps between installments. That’s why episodic series were the default for network TV until streaming services made serials “bingeable.” If you’re lucky enough to be able to play D&D with the same group several times a week, an epic mega-adventure will probably be great for your group. But for most of us, we’re lucky if we can consistently play once a week, and we accept that occasional absences will be inevitable. With a schedule like that, the chances of running into the dreaded “wait, what are we supposed to be doing here again?” moment are very high, and that is a major investment killer.
Is that really the case? Babylon 5 got the "pre-written ongoing plot" thing going back in the early 90s, and it was both pioneering and
highly successful, particularly given DS9 did essentially the same thing on a parallel run (albeit with less of a firm, specific sequence.) Followed up by a variety of TV shows in the late 90s and all through the 00s, like CSI, and what I have heard of shows like The Sopranos, The West Wing, The Wire, Mad Men, etc. Even children's shows got in on the game, what with
Avatar: the Last Airbender, and most folks know how beloved its long-term writing and payoff is. (It takes two and a half seasons for Zuko to get the redemption arc everyone knew he was being set up for, and it is
totally worth the wait, even for a child.)
Streaming didn't make long-form narrative suddenly viable. It had been viable for 15 years or more. Streaming just provided a new avenue of approach.
There's always been a place for both things. Further, the reception of things like
Lost shows how people truly wanted "an epic" as has been defined in this thread, and got very disappointed when all that build-up culminated in a hollow payoff, because the writers were writing it effectively module-style, by the seat of their pants, and could never generate a payoff that would match the hype they'd built. That is, it's quite possible for a group to be disappointed by a lackluster attempt to achieve synthesis and closure from a disparate pile of smaller adventures if what they really were hoping for was a well-executed long arc.
If folks show up for monster of the week and get metaplot (especially if it's badly-executed metaplot), they're liable to get bored or even annoyed that they can't do what they want to do: consider the negative response to the 2e Dark Sun metaplot. Conversely, if people show up for long-form narratives that pay off in satisfying fashion and instead get scattershot monster-of-the-week stuff with no linking thread beyond "these are the things we did, in the order we did them," again people are liable to get bored or annoyed that their experience feels like filler arcs and dicking around.
Are you confusing me with someone because of my weird new avatar? Do I need to change back?
You certainly don't need to change it back, but I
did need a moment at first. And I already knew it was you because I had followed a reply notification! That sort of thing happens every time someone familiar changes their avatar though. At least two other users come to mind that have made a change and I was mentally discombobulated. Such is the way of the (digital) world.