Admittedly, I know shit all about Scientology. The most research I've done into the matter was watching the South Park episode about Tom Cruise in the closet. So any references to Scientology or its beliefs went completely over my head.
But in the end, all that is irrelevant. The movie could be a blatant Scientologist's propaganda tool that doesn't pretend to be anything else, but provided it was entertaining I'd find something to enjoy about it. After Earth's problem is that it isn't entertaining. It's boring, there's nothing to enjoy, and it's not a movie I would recommend. That's the relevant issue here.