Although, in this version of things, she could still have Ben be something new to see on Tatooine.
My intuition about the whole ghost thing, ignoring anything other than the nine films in a vacuum is this:
Force sensitive people die and become one with the Force the same as anyone else, and this isn’t viewed as a bad thing. Ashes to ashes. Then, Yoda hears from Qui-Gon from beyond the grave. Evidently he happened upon some secret to preserving his consciousness in a way that still lets him meld with the Force. He’s not clinging to life unnaturally, it’s just… I don’t know, it’s serene or something. Anyway, he discovered this and it probably was an ancient thing he rediscovered. (This is an unknown ability up to this point at least as far as modern Jedi are concerned.) Qui-Gon teaches this ability to Yoda and Obi-Wan, and they are able to take it further by physically vanishing upon death and manifesting visually. This surprises Vader when it happens. When Anakin dies, Yoda and Obi-Wan (and perhaps Qui-Gon) help him to merge with the Force in the way they did. Anakin appears to Luke restored and fulfilled. Luke learns this ability as well, passing it to Leia and Ben Solo. Yoda gets really good at this, and hardly appears blur at all. He can hit people with his ghost cane, too.
Then, Rey gets the idea from what I can only imagine is the Jedi equivalent of the Bible that one can learn to hear the voices of dead Jedi. This doesn’t make apparent sense, given that when experiencing exactly this Yoda concluded Qui-again discovered immortality. But I imagine there must be some difference between the sort of vocal presence in TROS and true immortality.
Ugh, what a mess. The Jedi should just have had this ability consistently. But I still feel better maintaining separation between voices and visual appearances, as though up to that point the phantom four are perhaps the only four Jedi ghosts in existence.