Why was Cuvier's catastrophism model neither scientific nor a theory?

You can not have an intelligent discussion about what is or is not "scientific". One side of that argument bogs down in nonsense, the other side gets buried with insults. The only clear distinction is which side is supported by grant money. Cuvier made the mistake of mentioning something from the bible. Lyell rejected that and proposed an equally unscientific model, uniformatarianism. Lyell's model became accepted as consensus, and still strongly influences researchers even though it is obviously not so.