I was someone super compelled by it when it was just the original text-post / image, only to immediately drop any interest the second people expanded on it.
Word soup below, readers have been warned
I think something helpful to consider is Stephen King's meta-commentary on the horror genre:
“The 3 types of horror:
The Gross-out: the sight of a severed head tumbling down a flight of stairs, it's when the lights go out and something green and slimy splatters against your arm.
The Horror: the unnatural, spiders the size of bears, the dead waking up and walking around, it's when the lights go out and something with claws grabs you by the arm.
And the last and worse one: Terror, when you come home and notice everything you own had been taken away and replaced by an exact substitute. It's when the lights go out and you feel something behind you, you hear it, you feel its breath against your ear, but when you turn around, there's nothing there...”
He argues the latter is the finer of the three
I think liminality (transient, in-between spaces) lend themselves nicely to
terror quite easily. The original backrooms are liminal because they're non-places. They're hallways and empty rooms vaguely associated with the areas of old commercial and business enterprises that you were never really meant to be in nor had any purpose to linger around, and which aesthetically don't really exist anymore.
'Spaces' are distinct from
'places' in that places hold meaning for people, they have a purpose or significance about them.
Unfortunately, people on the internet kinda saw the word "liminal" and re-appropriated it to mean anything that feels eerie to them, maybe that and anything that also feels vaguely nostalgic at best. The 'pool-rooms' lack the same level of transience that the backrooms do as a public pool is a destination for people. As such, it isn't really liminal, unless you want to argue waterslides are (I personally wouldn't). Monsters are simply horror the second you try to define a perceived threat.
That and it just seemed to skew to a younger demographic pretty quickly after a certain point that adores stuff like fnaf. More concerned with gross-out / horror and the very basic premise of "what if innocuous thing... was SCARY thing?" which is probably why it just seems like stuff being thrown at a wall after a certain point.