>someone touched by Cthulhu and dealing with the drama of being tainted by an entity from beyond humanizes those said entities at some level.
I'm not so sure it does. If someone's infected with radiation poisoning and slowly dies of cancer, has the radioactive force become humanized? If an asteroid crashes into the Earth and kills us all, has it become humanized?
Lovecraft's fiction, on the whole, is about people being exposed to Reality. Whether it's Johansen and the crew of the Emma stumbling onto Ryleh and leaving mad or dead, or whether it's Armitage being confronted with the Dunwich Horror, the protaganist of the Shadow Over Innsmouth discovering his own truth or poor Nathaniel Peaslee being mind-swapped. The protaganists wander out of the comfort of our world and, for a moment, they glimpse the Truth, and whatever happens, they can't go back. Although the horror's cosmic, the results and the implications are profoundly personal.
Outsiders are people just like that, whether they were born into it, seeked it out or had it forced upon them, they've been exposed to the reality of everything. And that changes them, physically, mentally and spiritually. They're touched by those things you talk about, those things that can't be explained by magic, science or religion, and as a result, they begin shifting and warping to better fit with the reality they can now perceive. And they find themselves more and more distant from their old humanity. What they do then, is up to them, but they can't just go back to being a normal human being again.
Again, cosmic horror, personal consequences.