I see where you’re coming from and it plays well with “the jedi of the past” thing, but looking at it from a lore and canon perspective, it doesn’t make much sense to have Jedi other than Luke, Qui Gon, Anakin, Obi-wan, Yoda and (possibly Leia) communicate from the netherworld of the force without having discovered that knowledge.
It works because they’re not full-on ghosts. They’re brief voices.