Its lore breaking because Qui gon cannot become a force ghost, he was only able to become a voice, never able to fully become visible as stated in the clone wars.
Mace was never taught the ability either. And Ahsoka has never been shown to have died yet, the reason you can hear her voice is because the novelization shows rey was sort of looking into the world between worlds if that makes sense, so it would likely not age well.
I suppose you are right, but if I remember, didn’t Obi-Wan and Yoda help Anakin appear physically in the afterlife so he could see Luke and Leia on Endor? It’s possible that they could’ve helped the others as well. Just a thought, that’s all.