...as opposed to, y'know, the writing.
Is your plot the best aspect of your story? Should it be?
Let's get this out of the way: all stories need plot. And having a good plot is, well, good. Do you have a good plot? That's good.
There. Now we can move on to a bit of nuance. Namely, I'd like to posit that the plot isn't the most important part of a good story. It's probably not the first thing that will engage (or disengage) readers, it's not what elevates a story to being a Classic™, and it's not where aspiring writers should be putting all their energy.
Plot isn't everything
By definition, your plot is what happens in your story. At first, that may seem like it's the first and foremost aspect of storytelling. It is the story. But this is the trap that many writers fall into: the assumption that having interesting things happen is what makes a story interesting. In fact, that's the easy part. Anyone could conjure an interesting sequence of events.
Case in point: imagine a young child telling you a wild story. Maybe a dragon fights a giant robot; maybe a werewolf falls in love with a clone of Elvis; maybe aliens visit the planet and force raccoons to evolve into the superior species, giving them dominion over the planet. These things are, in and of themselves, interesting. But if they're told as a rambling, run-on chain of events that sounds like an incomprehensible fever dream--as young children are so apt to do--it's just not going to feel like a cohesive, well crafted, engaging story. At a certain point, you're likely to tune the kid out. Why? Because no matter how interesting the plot is, storytelling is all about execution.
So how does one "overrely" on plot?
My fear isn't that writers spend too much time or attention to their plot, but rather that they'll rely on their plot alone to carry the work. Personally, I spend a great deal of turmoil over wanting to have an interesting premise/plot and then a great deal of time outlining it. But even then, I recognize that the events themselves aren't inherently interesting to anyone else until I make them interesting. To that end, I believe that writers should see their style and voice as the ultimate selling point of their work.
I believe that writers should see their style and voice as the ultimate selling point of their work.
Moby Dick didn't get adopted into the literary canon because people were clamoring to read about a man on a boat (see also: The Old Man and the Sea). Even 1984, with a far more interesting premise, is just one dystopian novel among thousands. What set them apart, and what continues to set apart successful works, is literary voice. When a reader picks up a book and evaluates the first couple of pages, they don't care about the plot--it hasn't developed yet. They don't even care about the characters, who similarly haven't been developed. What readers will care about is whether the story feels engaging, and that all comes down to your voice.
So, here's how I see an overreliance on plot as a potential pitfall: developing writers will write for the plot. They'll write just to get to the next scene, or they'll assume that the events--simply by virtue of transpiring--are interesting. With that assumption may come a lack of detail, inconsistent pacing, an imbalance of dialogue vs. narration, or simply an all-too-straightforward tone that does little to engage readers.
The advice I'd give, here, is not dissimilar to the advice I'd give a young child recounting their rambling fever dream: start with the assumption that your plot isn't interesting by itself. I'm sorry, but that's the harsh reality of storytelling. Every story has already been told anyway, so realize the challenge is in the artistry of your voice. Realize that you need to make the story interesting in how you tell it.
Start with the assumption that your plot isn't inherently interesting [...] Realize that you need to make the story interesting in how you tell it.
Find your voice
I realize that the crux of my advice obnoxiously boils down to, "Just write better!" When put thusly, it doesn't sound helpful at all. But the writers whom I've seen improve the most are the writers who understand what to focus on. And--of all facets of writing--plot is not something with which writers generally need help. If you're feeling creative, then you can probably concoct an interesting (even complex) series of events. So, if you're just focusing on how cool your plot is while you write, you might very well be neglecting the writing itself.
To pull yourself out of this habit, consider the following activities:
Try writing about a subject that you don't think is inherently interesting, but focus on the quality of your writing. Utilize an engaging voice. Pull the reader into a rant, musing, reminiscence, or imagining about something that is only interesting because of how you tell it.
Try writing a genre that you don't normally write. You may not be invested in it at first, but use your unique writing voice to make it your own. (This is much like how readers aren't initially invested in any story until that story pulls them in. So, do that for yourself; make yourself enjoy the genre by writing it well.)
Find a story from another writer that you don't like. Analyze why you don't like it. What is it about the writing that doesn't engage you? Now, apply that same level of criticism to your own writing. Start looking at how you can improve the writing itself, regardless of the plot behind it.
Finally, read a book from one of your favorite authors, and pay attention to how they write. Ignore the story itself, if you want. Absorb the word choice, sentence structure, mood, pacing... just revel in the way that author tells the story. Emulate them if you want, or just adopt some of their tricks in your own way. The important thing is that you value the art of storytelling beyond the story it tells.
Happy writing!