So are the gods trying to get humanity wiped out
Trope/Plotwise there's many ways the "celestials" can...use... humans. Certainly not as equal partners, but definitely as agents of their will.
The huge lore dump established the "celestials" are diminished in power, so presumably cannot act too directly in the world.
The human/dragon pact seems to be a major hindrance to them, as they're dead-bent on breaking it. Could be, because as shown, humans
can learn "draconic" levels of magic. Or at least a sufficient number of them to be a threat to the "celestials". Not many dragons, but large amounts of humans. Who seem to have forgotten "some basics" over time. There's definitely a "Lost Lore" plot thread running.
There's a lot of
very Asian things going on in this story that ..doesn't translate quite well to Western European..
I think the translation of "Dark/Demon" Gods is fundamentally flawed, especially given what is in the lore dump we got. It's just that there simply isn't a proper western equivalent.
I think the closest we have in western mythology is the opposition of the Jötunr ( as embodyments of natural phenomena) versus the Alfar ( embodyments of the Ethereal ) in Nordic mythology.
And no, the Alfar/Fae were
very much not nice , nor were they on the side of humanity (Aesir/Vanir)... Only their own, ever.
(Edit: currently, to my knowledge, the
only Manga that conveys how bloody dangerous Fae/Alfar are would be Magus' Bride. And that one's Seinen for a good reason..)
It's funny how a light story about your usual OP protag running into Tropes still has some pretty deep background regarding current and past cultural ...associations...
Let's just hope the author doesn't bugg'r things up.