People often use the term "soap opera" to refer to a kind of storytelling, but it seems to me they rarely spell out what they mean in a clear, useful, way.
In trying to do better it may help to consider the fundamentals of "good," dramatic, conventional storytelling in the Western tradition going back to Aristotle and since developed by people like Gustav Freytag.*
From such storytelling we expect a story to be a "completed action." We expect a unity of "time, space and action." The result is that we expect that of the cast of characters one will clearly be protagonist; we expect that there will be a clear, main line of plot development; we expect the details to all matter (in line with the principle of "Chekhov's gun") as we proceed from exposition to rising action, climax, falling action, denouement--and beginning, middle and end.
This does not wholly exhaust the standard, but it is what is most important in it for explaining how the soap opera differs from it, because it lacks all these qualities. Rather than that completeness and unity of structure with its requirement of some measure of tightness of construction it is apt to be rather loose--a "loose baggy monster" if it goes on for long. Rather than having a clear protagonist it is about a bunch of people of whom one is unlikely to be, or remain for long, clearly more central than the rest. There may be a starting point--but there will not necessarily be an end, and hence no middle, because what the narrative does is follow those many people not through one big action, but an assortment of different, perhaps unrelated and nonsynchronous actions likely to involve some and not others one after the other (with, it might be added, many actions making little to no difference in their lives because the show must go on, so to speak); while if there is an end it is more likely to be a matter of the writer ceasing to follow those characters' doings (even if he comes up with an end point for them that makes their ceasing to do so look logical) than because some trajectory starting at the beginning has satisfyingly run its course by this point.
In short, soap opera is fundamentally different from conventional, unified, plot pyramided beginning-middle-end-type storytelling--with, I want to stress, the accent properly on different (as I have no interest in getting into the issue of "worse," "as good," "better" here).
As the reader may have guessed from this, while we call this storytelling mode "soap opera" this is only because soap opera (a term originated with radio shows) tends to work like this, not because soap opera invented this kind of narrative, which we are apt to find plenty of in nineteenth century novels, for example. (The term "loose, baggy monster" comes from Henry James' characterization of War and Peace, which I think can fairly be called a soap opera in the sense in which I use the term here--the more in as Tolstoy intended it to be just part of a far larger saga.) Moreover, if the kind of programming we associate the soap opera with, the daytime television soap opera, is one in deep decline these days amid the general revolutionizing of media in the digital age, this kind of storytelling is still fairly widespread--the more in as the looseness of the format is such a convenience for executives handling messy productions, eager to keep writers on a tight leash, and ever happy to spread out and drag out their tales with extra seasons and sprawling shared universes for as long as they remain profitable. Episodic television generally works that way--and so do the many movie franchises that, as they become more prolific, function more like TV shows than movies or movie series'. Indeed, the Marvel Cinematic Universe can be taken as a soap opera--while in Disney's hands there seem to have been notions of turning the storytelling of the Star Wars saga into a soap opera.
As all this makes clear, people do enjoy soap opera--but sometimes taking this approach proves very ill-advised indeed.
* Even if you've never heard of Freytag you probably know Freytag's explanation of plot structure (popularly known as "Freytag's pyramid").
Book Review: Providence by Max Barry
4 hours ago