So, first of all—pleased to meet you; and to have an opportunity to dig into this issue a little further.
To begin with: by rights the statement “It’s not that simple” ought to be reassuring rather than otherwise.
While I was storyediting, back when dinosaurs walked the Earth, some of the writers I invited in to pitch would bring me surprisingly good ideas with a near-hopeless air that was frankly heartbreaking. “This is all I’ve got,” they would say, expecting me to chuck them out the door. And it was so often my pleasure to say “No, sit tight, this story has good bones: let’s see if we can rearrange how the flesh goes on them.” Then we’d get to work, and those were some of the strongest scripts of our sixty-five.
And routinely, when the work was done and we were all communicating in a more relaxed way, I’d find that—animation being an area where a lot of newbie writers cut their teeth before going on to live action—a lot of my newer writers had run into a diagram like that. Some of those diagrams were better than others. But the flatly reductive ones that simplified story arc in the manner of the one above, and did not make it plain for the beginners beyond any possible misunderstanding that this is only one paradigm in which you can proceed, were the source of the worst trouble.
The often unseen (and I’m sure unintended) result of such diagrams, therefore, can be to keep good stories from being told because their potential tellers can’t see how to make them fit into what’s been set out for them as the way things have to go. And if people think that the realization that “there have to be other ways to tell a story” would be obvious to everybody, my lived experience has proven that assumption tragically incorrect. I was storyediting some very smart people, and they didn’t get it until it was forcibly pointed out to them that there were many other acceptable ways available to construct the story that underlies a screenplay (or any other).
(The above chart is also, unfortunately, very Western-centric. Styles and paradigms of dramatic structure vary wildly worldwide. Some of the best writing being done right now in both prose and film is by people working outside that structure, purposefully subverting it, or importing elements of other structural paradigms into the Western one with an eye to gradually transforming it from the inside out. So to omit an acknowledgement of the local nature of such a diagram is, at best, kind of careless.)
Something else that bears mentioning here is the ungodly mess that followed Joseph Campbell’s media-borne discussions with George Lucas on the “Hero’s Journey” concept from Hero with a Thousand Faces. The Journey got seized on with terrifying enthusiasm by Hollywood (and other screenwriting/storytelling regions worldwide) as the Hot New Thing. (Not least, I suspect, because “Hey, look how it worked for George…!”)
As a result, new novelists started discovering that it was hard to get a book sold unless it conformed to the Journey. (Fortunately this problem seems to have largely died off: but while still in effect, it was damaging.) And for a good long while you could not get a screenplay over the transom anywhere in the US film market unless it could somehow be made to fit into that paradigm. The slavish slapdash employment of it as a sort of panacea or Guaranteed Highway To Success was something to behold, as scripts that did not fit the Journey “correctly” were brutally reworked, with all the bits of them that didn’t fit lopped off in genuinely Procrustean fashion. Writers unwilling to submit their ideas to this process—and there were a lot of them—didn’t get their stories told. And until the fad subsided, a lot of newbie and seasoned writers’ stories that “didn’t fit” were strangled in the cradle by uncritically accepted versions of the Journey diagram. More recently I’ve been willing to joke about the subject now and then… but there’s always a shadow lying in the background of the joke.
So, the tl:dr on structure-of-drama diagrams in general: I think they can be helpful if thoughtfully and explicitly annotated (for the sake of the new kids) that what they’re looking at is a broad generalization with many exceptions, and not to be taken as The Rules.
Now, moving on: sandcastles. If you read that phrase as somehow derogatory, that’s your construction, not mine. Sand castles as a metaphor for the “germ matter” of vision are way older than I am. I built a whole lot of those sandcastles myself, thousands of them, in my head and on paper, for many years before it ever occurred to me that I might ever get anything published. And I’m still building them now, every single day.
They’re also, however incidentally, a sideways metaphor for persistence in imaginative work. The waves (of circumstance, or changing-your-mind, or just plain realizing your story’s not working) roll in over your castle and destroy it? Fine. The sand’s still there. You build another. And another, and another, until, as you go along, you find a way to do it that’s more resistant to the sea of Story. A lot of useful (storytelling-)structural work can get handled during that process, as you learn and learn by trial and error what works and what doesn’t: what holds up, as you test it in your imagination, and what collapses.
All the good things ever made have started with that imaginative process, and its (inevitably) repeated failure under test, and the persistence of all the imaginers who just kept coming back to a given plot or invention or other idea until it worked. And that’s the persistence I had in mind. Without it, nothing good happens. It’s essential. The sandcastles, and the skill of building that you learn from them, and the stubborn insistence on (as soon as you’re ready) building another better one to replace the last one that the waves took away, are at the very core of it all.
Meanwhile: Everybody walks their own creative road. All of them are valid. Whatever shape it takes, I wish you success and satisfaction on yours.
(PS: I’m sorry about the ellipsis. It’s a tic, and I’ve honestly been trying to cut down.)