Religion is just a sense of gratitude for existence, plus the idea that the cause of existence has a personality.

That's isn't exactly right, though, because the act of gratitude is already by its nature directed towards a person. It's not an idea, it's an innately human act. If you are an atheist, you can say that we feel gratitude because we are confused about causality, but you can't stop yourself from having that feeling sometimes. Would you want to?

The interesting question to me is, can you accept the validity of the feeling of gratitude while at the same time denying its objective rationality? Can you say, "there is no person to whom I can be grateful for my existence, but my feeling of gratitude for existence is nevertheless valid?" If so, what is this validity?
@amos maybe religion does a job of putting a face to the name of gratitude which we innately feel at times. I suspect, at least some of the time that religion hijacks that gratitude and directs it to its own ends, preventing whatever productive, transformative change it could otherwise catalyse in a person or society.

@the_elite yes, I think it's true that the feeling of gratitude gets hijacked, but I will insist that it is not religion itself which does that. It is the drive for power in the guise of religion.

On the other hand, I have to acknowledge that because of the success of this hijacking, much of what has succeeded in getting itself called "religion" is really to blame.