In the old days, the dimensions of a television series was dictated by the scheduling of broadcast television. 21 or 42 minutes per episode, padded with commercials to make 30 or 60 minute broadcast slots. American television contained 13 or 26 weekly episodes per season. Generally speaking, a single episode was a designed as a fully-contained three-act story, with occasional two-part episodes. The cliffhangers that had been common in radio drama were carried over into the early days of television, but those mostly fell to the wayside. In many cases, a small amount of effort was given to character development and even character story arc, but the main story structure was wholly contained within single episodes.
Streaming television has freed television from the rigid dimensions of broadcast television. Episode length can be as short or as long as necessary. The number of episodes in a season can be whatever makes sense. Viewers do not necessarily need to wait a week between episodes. This has unleashed television writers and producers to experiment in all kinds of ways, and I would argue that what has emerged is a new format, which could rightly be considered a new art form.
A single story can now be told across an entire series. This makes the format longer than “film”, which has an average length of about two hours. This offers the possibility of significantly more depth, more detailed character study, and more complicated story. Yet in most cases, some adherence to the three-act episode is retained, leaving the viewer satisfied with the resolution of the episode story, but still eager to continue following the overall story of the season or series.
This means writers, producers, and show runners must make a number of creative decisions about how to balance episode story with overall story, and how much depth to devote to each. Have we been doing this long enough to know what works? I don’t think so.
Writers and creators are faced with a market that demands new television concepts with season-long stories baked in. That means character and story arcs must be planned in a fair amount of detail at the beginning, with at least some initial episodes written (as scripts or synopses). This is a much higher bar, but of course it has the potential for a much bigger pay-off.
Update: I guess it’s really not that complicated. In writing, there are goals at every level. There is a story goal, there are scene goals, and there are character goals which may not be satisfied within the scope of a single story. In a series, there are episode goals, season goals, and series goals. Each episode has a beginning, a middle, and an end, even though season and series goals may not start or end within the particular episode. A season has a beginning, middle, and end, and so does a series (unless it gets cancelled). The real choice for show writers is to decide how much emphasis to place on the various storylines: episode, season, series, and character arc. This isn’t a new concept; there have always been secondary storylines in episodic television, and there must be a balance between them.
Update: I was just watching an episode of “Better Call Saul”, and it definitely didn’t have a beginning, a middle, and an end. It progressed the story, but nothing was started or wrapped up in the episode. Perhaps I noticed because I was only watching a single episode, and not binge watching.