Often I use the term, 'storyline,' when referring to mss. The recognized industry term is 'plot.' Plot is more than a beginning, middle and end. It is more than the outline from which the story is built.
Plot is the most important element of fiction writing. The plot has to deliver for the reader to feel satisfied with the story. There are style expectations for each type of plot. The reader expects those elements and it's the writer's job to deliver.
First time writers who haven't studied writing often forget about the reader's expectations and the industry demands while in the midst of the feel-good high of writing. I would submit that there is a bio-chemical/emotional high to writing that is as addicting as the one people who exercise feel.
The point of writing, the craft of it, is the reader and the integrity of the art. Much like photography where anyone can take a snapshot with their phone, that doesn't make it a professional photograph (and don't get me started on photoshopped images).
Just so you know how this all fits together, the second important, nearly equally important, element is character. Characters have to have dimension. In one of the first writing classes I took, one assignment was to categorize a list of characters in a story [we read] as flat or round. The character's action and words (dialogue) fill in the life breath to make them real for the reader. By the way, there needs to be a balance of both types of characters in the story.
If there is no plot, the story is simply a collection of words that recount an event in part or in whole. That is largely why I'm not a huge fan of memoirs. Unless well done, they are [to me] much like reading a history book and it isn't a shared history, so why should I [as the reader] care?
There are lots of books on the subject of plot development, here is one I recently read: 20 Master Plots and how to build them by Ronald B Tobias, published by Writer's Digest Books. If you're looking for writing resources, check out Writer's Digest Books. Most of their books are pretty good. A few, I found to be dry reads. Also, shop around and price compare. I found substancial discounts by doing that. Be warned, though, their book list is like sending a kid to a candy store with $10 in their pocket.
Just to cover the legal requirements, I have not been compensated monetarily or in kind to mention the book, author, or publisher in this post.