My favorite part is that you realize their are plenty of stories that contradict your point, but you dismiss them as simply being wrong. To that I say...
Nuh-uh.
Vampires throughout fiction have represented desire, power, disease, alienation, mental illness, addiction and much, much more. The monster vampire is only one use for them among hundreds. And every living being lives at the expense of other living beings. Life if brutal and harsh. You and I are the most dangerous predators on the planet. And while all life feeds on life, as intelligent creatures we do try to carve out an exemption for things like ourselves. So the question is were the Endless people and they were and they made it several hundred years feeding off the aether of those who died of natural causes. It seems given what there were there were a multitude of ways to change their dietary needs (or eliminate them completely) that we didn't bother to explore because it was time for a trial.
If you presented me with just the facts on paper, I would assume your assessment of what they are is entirely correct. The problem is, I played DT. Up until DT, I would have assumed the "spark of life" was part of the soul. But DT is an expansion where souls are coins and everything that makes a person a person seems to be part of their memory aether. The shades in Amaurot are not self-aware, except for maybe Hythlo's and I would object to destroying Hytho's shade for being "twisted and unnatural." That shade has done us quite a few solids and isn't hurting anyone.
The people in Living Memory are very much self-aware. They aren't just running off a script. They have thoughts, they have opinions, they can get bored, they can lead a rebellion orchestrating their own destruction out of prejudice. They are feeling, thinking people by every metric of measurement I'm aware of. There are so many instances in Living Memory that debunk the theory they are just the most convincing bots ever created from literally viewing Otis's thoughts thus KNOWING he has thoughts to the tour guide approaching us and assuring us that everything should feel the same as when we were alive. If everyone is being controlled by a system, he should be aware we're not on it, and why would the system be assuring itself it feels the same. Heck, why would a system of bots be sitting around interacting with other bots for all eternity anyway? Without the Endless being sentient, Living Memory makes no sense.
I'm fairly confident the writers didn't fully consider what they did here and wrote the Endless as 100% convincing people in order to get some tears out of players when they later off everyone's mom. But from what I can see in DT, your mind is with your memory aether, not your soul.