And that in fact the original Doom had: stumbling around a maze trying to find the way forward is a huge mood-killer no matter how cool your set pieces are.
Also, I keep reading people saying things like "I went down a MyHouse rabbit hole and now I want to read House of Leaves." I've got a take here too! You don't want to read House of Leaves. You want to read Subcutanean.
The game snubs legibility — the basic mechanics of progression are not just arbitrary, but deliberately hidden. You often progress by accident and even after are unsure what you did. Some clues exist, but rather than being foregrounded they are left in easily-missed margins along with a mess of insignificances, and they're ambiguous and hard to interpret even when you look right at them. This means the player must take recourse to guesswork and brute force, or to some form of asking someone who's already figured it out.
Under most rubrics, this is the very essence of bad game design. Any point-and-click adventure that works this way is generally considered botched infuriating trash. But myhouse.wad is a sensation! People love it! Indeed, if you read back the Doomworld thread, you'll see that this very obscurity is THE thing people love, even above the horror trappings. (If anything I think its overt creepypasta-isms are the weakest part.) It's not a mood-killer, it is the mood. When you have no idea what's happening, what could happen, or why anything happens, you get a vertiginous sense that anything is possible, at any moment, for any reason. This in turn inspires a giddy excitement to explore and find out all that is possible. And there's also a whole communal aspect: the internet exists, and Doomworld and the Doom Wiki are lively. Whatever somebody finds, they write it down and share it, and with lots of explorers working together, you can be sure that eventually everything will be found, even that maze that only spawns like 1 out of 116,000 times. It's more-or-less the Tower Of Druaga model.
Does this make it a less effective horror experience? Yes. But one huge obvious instance aside, myhouse.wad is spooky more than it is scary, surprising more than unsettling. It's not aiming to induce fear and sleepless nights in the player. It is pitched as a horror ARTIFACT, a haunted cartridge the player curiously examines and thinks about from a distance, rather than a story the player is sucked up inside of.
bad game design is sometimes the most soulful one. in fact, i wish myhouse.wad had more of this shit and less of the liminal stuff lol.