Was returning to the moon a metaphor for dying/leaving for heaven?

Yes, IMO. I saw it sort of a suicide. And the regrets for the life you could have had if you gave it a chance.

It could certainly be interpreted that way.

Can't stop the signal.

Yes! Oh my gosh yes. That was my first strong impression. The cycle of life/death/reincarnation that occurs for the souls of the material world. That was her returning to her true place in the heavens, perhaps the place where the soul returns to until it is reincarnated again. It is different for her because she is a heavenly maiden/goddess who had to return with her people. The whole movie to me was the culmination of that, the journey of the soul and the quest for "enlightenment" (here meaning a soul that has realized its goal in its current reincarnation/learned its lessons)/happiness, which was her goal. To be truly alive, which seems to be to be the nature of the soul here on earth, to experience life in its natural beauty and wonder, to rediscover our connection with the natural world and the flow of life when the soul is in its natural state.

No not at all. In the original fairytale, The Tale of the Bamboo Cutter, Kaguya was not of this world. She was a 10th century alien. She simply returned from whence she came.

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I saw it as an interpretation of Buddhist reincarnation. That's why Buddha was on the cloud. The gifts that came after her escape (gold and garbs) through the bamboo were given to the old man knowing he'd make her life unbearable enough to have her go back. She also grew quickly because she was so happy in nature but never got any bigger in the materialistic environment.

Also, think of it as someone that died and got the chance to comeback and relive (she became a baby once she touched the woman (mother nature))a new life. She knew that her life away from the simple things (again, Buddhism) was killing her heart and that her second life was being wasted as a "princess".