You're right in the sense that it tends to be hard to understand things when your salary depends on you not understanding them. This seems to describe most web developers from the number of non-compliant consent popups in the wild.

Can you give an example?

If your claim is that sites that use cookie banners don't understand the law, I don't know how we square that claim with the European Commission site's cookie banner. Certainly, the government itself can interpret the law successfully, right?