The force ghost thing works fine in the original trilogy because the original trilogy is a fairy tale. George forgot Star Wars was a fairy tale when he made the prequels.
Force ghosts don't need an explanation in a fairy tale, because it's a story telling device. We don't need to know how it works, just like we don't need to know how lightsabers and spaceships work. They're magical things in a magical world that exist to serve the story being told.
I really wish George hadn't muddied the pure fantasy water with his psuedo-scientific mumbo jumbo in the prequels.
Actually, I really wish he'd never made the prequels. The psuedo-scientific crap is just one thing on a giant steaming pile of things that never should have happened.
In my opinion.
I might not have minded it IF it was shown to simply be the perspective that the Jedi had at the time, and related to their own downfall. Like, they got too tied into sciencing their Force stuff and, as a result, became more disconnected from it. They became too dispassionate, too emotionless, too unable to feel wonder and magic and the like, and instead turned their connection to the Force into something that was decidedly not mystical.
Example: midichlorians. You can rehabilitate midichlorians...pretty easily, actually. You just say that they are a correlative effect, rather than a cause. The Jedi look at them and say "Ah. you have more midichlorians, and you are stronger in the Force, therefore midichlorians make you strong in the Force." Which is dumb, because then people would have Force abilities thanks to blood transfusions. (Actually, that could be really cool, but that's not the story and I digress.)
Instead, you could simply say "No, the midichlorians merely congregate in people who are strong in the Force. They don't actually do anything with the Force at all. They're just....there. Their presence indicates Force strength, but doesn't cause it. We don't know or understand the cause."
There. Boom. Problem solved. Jedi got dumb and thought it was a science-y answer, and it turns out they screwed up basic cause vs. correlation and the real answer is back to being something possibly mystical. AAAAAAND that's a big part of why the Jedi Order fell. The PT could've steered into that. Or the ST. But...they didn't. Instead, it just feels like this jarring thing that George stuck in because it was in one of his early drafts and he liked it for the time period when he made the film in 1998/1999.
...And then Anakin just knew how to do it 'cause he's the Chosen One?
Another of George's changed premises. Back then it was just something all Jedi did upon death, per him. And, like so many other things, a decade on, he "always intended" something else entirely.
Two things.
1. About George's intent? You know what? I don't care. I literally do not care what his original intent was anymore. It's so amorphous and changing that it doesn't really mean anything. Regardless, while an author's intent is relevant to interpreting a text, I would say that ultimately, the text has the meaning ascribed to it by the audience. So, George's intent doesn't really matter in the end. It's a footnote. Interesting in terms of understanding the creative process (insofar as it helps with that), but otherwise irrelevant.
2. George's "original intent" is whatever it needs to be in the moment. And the thing is, even when he changes his stance, he's probably still technically correct. Given how many revisions Star Wars went through, and how many alterations there were in that process, it's likely that everything we saw that was created by George himself is a part of at least
one of those versions. So, like, "I always intended Vader to be Luke's father" is true...starting around revision 4 (or whatever). But there's also another yellow legalpad that has Vader as a separate character from Luke's father entirely. And there's one where midichlorians are the source of the Force, and another where it's a mystical energy field, and another where it's something literally everyone can do, but some can do it better for unknown reasons or whathaveyou. In other words, there are enough versions of "Star Wars" in George's head and on paper somewhere that "original intent" becomes functionally meaningless. And as I said, it's all still beside the point.