they are expressions of a shared humanity.

Of course they are, I'm in complete agreement here. People all around the world tell myths and they describe universal human experiences. People around the world have a great deal of experience in common. One of them is telling stories where characters in some way represent big ideas, superhuman forces of the world, or great human figures renamed. There are other good uses for the word 'allegory' but this correctly describes the form of so much of myth.

I really would never describe them as

just "a bunch of allegorical stories about why the sun rises every morning".

at all. On the contrary, it is noteworthy in it's universality. But it's not the only kind of storytelling, and not the only universal kind, and it is certainly not the only universal kind of art. So I think it's not watering anything down or doing either of them a disservice to make the distinction this way.

Anyway, despite disagreeing with you I want to say I do respect your opinion, you've clearly read and thought about it a lot, and I think it's a valid position to come to. Agree to disagree I guess.