As with the usual rules of expositional infodumping and inorganic plot points, I believe that there is more to a shitty plot than simply ticking aspects off a checklist. Before I deem a plot shit, at first I try to identify a focus. What is the author trying to achieve with this plot? What message is the author trying to relay in this plot? What kind of medium is the author using to achieve their goals?
Allow me to go off a tangent and elaborate on my third rhetorical question. Say, the average Call of Duty. The plot is often lauded as a railroad that deserves no focus besides being able to serve its purpose of giving the player reasons to shoot shit. However, I beg to differ. Yes, it's nothing but a railroad, simple-minded shootfest. HOWEVER, it gives the players ample motivation within the story that is easy to digest and doesn't rip the focus away. The writers understand how to make interesting characters through simple dialogue (Cap. Price, Woods, Ethan) and light story with lore to serve as motivation (In the first Black Ops, you were brainwashed with numbers that could lead to the US getting chemically destroyed. The story itself is simple, but every character has intel weaven into the exploration aspects in the missions itself if the player so chooses to investigate them. The choice of discovering the lore isn't crucial to the enjoyment of the plot, but it is a wonderful side dish to enjoy.) Character developments, though minor, happen organically within story events, and rarely do they need heavy, exposition laden cutscenes to give context on what you're about to do (KOJIMA *cough cough* Death Stranding is still good though)
That, to me, is a good plot; within the medium of video games, that is. It understands that the plot operates, first and foremost, for the gameplay, and does a good job at creating scenes that help amplify the "game" part of a video game. Imagine if Call of Duty had Schindler's List as a story. I wouldn't call it a bad story, but as a video game plot; it's terrible. Characters may be deep but so much of it requires deep character interaction and intricate scenes that, in a first-person shooter, simply wouldn't work. Now if Schindler's List was a point and click adventure game, then that'll be a different case entirely.
Of course, there's more nuance to this, but I'm getting out of hand here.
To deem a plot good or bad, I'll have to identify what the story is trying to do. Say Black Lagoon; it's a story where mercenaries kick doors down and shoot the fuck out of people. The focus, first and foremost, is animated action, and the plot accommodates it spectacularly. Rarely does characters ever give exposition and even if they do, it's in spades and doesn't interfere with the rest of the running plot. The characters are charismatic enough to enjoy their company and the events that unfold, though outlandish and senseless, goes in line with the tone that the focused action aims to present.
Now we'll take that comparison over its head and take a look a Goodnight PunPun. Those who've read it; you know. The plot is slow, and rarely explains itself, opting to show a lot of things unexplained and very abstract. The characters are pieces of shit, and the dialogue just rambles on in introspective bullshit and depressive sandwich. However, that is the point of Goodnight PunPun. It's a study of broken people held by childhood promises and bad decisions, chained by regret and their struggles to fit into society's perception of right and wrong. The aim is to show broken people trying to make the best out of a world they can't comprehend or, at least, cooperate with, and trying to justify their terrible actions in the name of self-serving salvation. If Goodnight PunPun's plot was used in a fantasy action manga, it wouldn't be a good read, because the character interactions would have to be pages after pages of exposition detailing their feelings and thought as Pun²'s plot simply cannot accommodate action scenes at all. The story will still have its merits on its attempts to craft a study of human regret, but its execution would drop it down to a notch too low to perceive its potential.
My point is that, a plot isn't a singular entity that drives its focus or medium. Everything plays with one another like an intricate orchestra. The plot would be pointless without a good focus, and the plot's focus wouldn't be conveyed effectively without a suitable medium, and a medium needs a good plot to be enjoyed to its fullest. However, a plot is an important backbone to this dynamic. No matter how thoughtful your focus may be or how innovative your medium is, if your plot cannot peacefully synchronize with one another, the experience would be dragged down heavily. If that happens, it's safe to say you've got yourself a bad plot in your hands.
