On the same topic, what exactly is too "rich" about Evo?

I see it mentioned a lot with people who turn to it, and they mention, "It's too rich for my cat". What does that mean, what specifically is too rich?

Too rich in protien? Meat? Fat? Calories? Just wondering, because if a kibble is too rich, then wouldn't a raw ground diet be too rich as well?

If anyone has any insight, I'd appreciate it.

I mean, his activity is much improved, his fur is super silky /no dandruff, he loves the food, his stool is not too soft, but not too firm and smaller (he eats almost half of what he used to, about 1/3 cup daily, IF that)...

It's just a stink! LOL