Had been thinking about this post (which is a fake excerpt from an imaginary narrative written to mock 'tumblr prose'), and how most "no actually this is good" comments are highlighting how the construction of individual sentences is interesting, how some of the language is evocative, how it Goes Hard. Because that post is written badly in a very thoughtful manner that focuses on core structural issues rather than going for low hanging fruit of poor technical proficiency with the written word, it is not bad in the most "obvious" of ways. So I think this is a legit learning opportunity, but also I don't want to dunk on anyone so instead I will just preach to the choir of My Followers.
But yeah like to be more constructive than "lol tumblr prose bad", really the issue in Large part that characterizes "tumblr prose" (which to be clear I don't think is a discrete thing and at most is a combination of several writing tendencies influenced by the medium of Online) comes down to the lack of real contrast in Any aspect of narrative construction, and an obsession with being quotable and constantly being at 100% of Going Hard (which go hand in hand).
In that post, the character voice is indistinct from that of the narration, and the characters quote one-liners that look Meaningful as excerpts and are borderline nonsensical as dialogue. There is no more than the faintest, most generic hints of characterization; these people exist as vague concepts to say deep words for the reader. The sentence length has little variation from its staccato beat, and so it is awkward to read and fails to complement the action or accomplish anything with the pacing (save for the slight slowdown when the torturer feels all that damp animal electricity). The timing is awkward and exaggeratedly dramatic. The description is a flowery kind of tryhard visceral and seems avoidant of describing anything too directly ("something dark and arterial" where there's nothing being accomplished by conveying uncertainty about what is currently gushing out of the injured character and the simple use of "blood splashed across the stones" would actually be 10x more effective), in a way that does disservice to what is supposed to be a torture scene, and leaves it weightless and ungrounded. In fairness to the people saying "this is good", that is MUCH easier to say when reading this fake excerpt as the standalone piece it actually is, but this kind of writing Cannot function in an actual narrative and is not what an excerpt from well constructed narrative fiction is going to look like basically ever.
It reflects a lot of very typical amateur writing issues that just about everyone has to grow out of (the minimal diversity in sentence length, non-attention to scene pacing and timing), and issues common to fanfiction-influenced writing on social media (allergy to paragraph lengths of more than two sentences, little to no description of the characters or setting because, in fanfiction, the reader already knows their physical characteristics and mannerisms and it doesn't need to be lingered upon, Unlike In Original Fiction). But this particularly hits on an issue I think is semi-unique to narrative writing in the social media milieu, which is a focus on being quotable. This may not even be a conscious impulse at all But It's There. This kinda apparent terror of any moment not being as beautiful and hard hitting as possible (or for comedy, any moment not being A Joke). Everything "Goes Hard", so nothing actually does. A lot of "tumblr prose" type writing is less a narrative, more a string of quotes loosely assembled into narrative that vaguely gestures at things like Plot and Character. It substitutes depth for Suggestions of depth by utilizing stock symbolism without building it into the narrative, and by gesturing at weighty contexts without actually engaging with them. There can be little contrast or effective use of tone, pace, description when your story is a series of Hard Hitting Quotes.
I'm reading Watership Down right now and I think it's a great novel overall and can work as an example of how important it is to utilize contrast in your writing.
This segment is the lengthy first description of the titular down, which the rabbits are now encountering for the first time:
Adams is slowing the pace here to introduce us to the setting of the next segment of the book. The average sentence length is very long and keeps us lingering in the sensory detail, while still varied and thus smoothly readable. This new place is introduced by simultaneously conveying its physical description in vivid detail and conveying its feeling and character, and getting the most out of every described feature to do so. The thorn trees are "wind stunted". The air is "scented". The language takes on a very flowery character and heavily utilizes simile and metaphor. Woodland is "tumultuous with evening", sunlight filters through grass "like a wind" to the small creatures below, in contrast to laying "like a gold rind" on the hill when seen from a distance. This grandiose description is heavily functional and conveys both exhaustive physical detail and a feeling that this place is beautiful, awe inspiring to something like a rabbit, and full of life, though not without quiet hints of danger. It hits because Not Everything In The Book Is Described This Way. It means something that we're lingering like this and stopping to get a sense of this place on every possible level, and moving away from more direct, simple prose to convey the feeling of the place in depth.
This segment describes the rabbit Bigwig being found caught in a snare:
The prose here here has the opposite approach of the first excerpt. The language is concise, direct, and brutal. It only veers slightly away from the literal to describe Bigwig's voice as 'bubbling out' from his mouth, both conveying that the saliva and blood in his mouth is literally bubbling as he speaks, and implying the unsettling way his voice sounds as he's being strangled. The sentences are much shorter on the whole, as fit for the pacing of a tense and rapidly changing scene, and the pace closely complements the action - "There was a pause" not only conveys That There Was A Pause but interrupts the rhythm of this segment; the moment of uneasy stillness is echoed in the act of reading itself.
The scene this is excerpted from is extremely effective and does in fact Go Hard, it's well constructed in of itself but its effectiveness mostly lies in its place in the narrative. It's the culmination of a long, tense buildup as the reader becomes more aware that something is deeply Wrong about the place the rabbits are in, and the payoff is effective in being blunt and visceral, which hits because Not Everything In The Book Is Described This Way. Nothing about these excerpts are particularly quotable because that is actually not what good narrative writing is about.