Speaking specifically in regards to the Oreo knock-offs. There are a lot more differences than there are similarities.

What's the rule here, an Oreo competitor can't have a blue rectangular package? It can't have cookies with words superimposed on top of them?

Let's look at what is different, Aldi's brand has: No Oreo branding, no milk, and two cookies instead of one.

The Nutter Butters one is the most ridiculous, there are so many differences: Nutter Butter branding, two entirely different shaped cookies instead of one peanut shaped cookie, and the addition of about 7 peanuts spread out over the package.