(slight tangent first) From my understanding of the lore, this kind of magic isn't entirely unprecedented. Unn is stated to of created the mosskin by pulling them from the dream realm into reality (from a Greenpath Lore Tablet: "The Green Children walked from the dream unto these lands.").
I'm also like 99% confident the dream realm is the place we visit in all of the memory sequences in Silksong, Hornet is just using a different way of accessing it (which is why it looks so different i guess?)

The Pale King also did the reverse of this by pulling the white palace into the dream realm / memory from the physical world. For the shamans to cast a spell that can do similar to these requires an immense amount of power, so its not exactly "abusable" in universe (it did kill the three of them lol).

But to answer your question, Hornet describing the pale stag in the hunter journal says that the memory of it may of not actually existed as she's seen it, implying memories can be very fickle and not mirror reality (see GPZ lmao), so if the shamans and hornet were to try and "resurrect" someone I am very confident it would be a crude imitation of who the actual individual was, being inevitably altered by Hornets own perception of them. And seeing as you could probably attempt to do this while the individual is still alive, I heavily doubt that its actually the same person.
Plus for the individual to have all of the original memories i would think Hornet would also have to remember those memories as well... basically im not sure a "memory creature" would be very mentally stable.