Came out of the woodwork to say this is dumb.
Mama was also called a thing and beast, so much so that Oda had to go out of his way to actually say she was human due to the nonsense. So I totally believe Kaido is a regular human. That’s not a stretch to even think anymore seeing as how we have ample evidence of godlike humans walking around the planet already.
Besides, the technology for an inanimate object to eat a Devil Fruit didn’t exist until Vegapunk created the means. It was already mentioned way way in the beginning. So there’s no actual way to say that Kaido is a Poneglyph turned living being because, well, if the timeline is correct Vegapunk didn’t invent a way for that to have happened yet.
We also don’t know that Roger read those poneglyphs himself. During his time, plenty of people were alive from Robin’s island that could have just jumped on his ship to help him. We don’t know all of his crew so the possibility is still likely.
So in conclusion: Stop it. Get some help.