Most EU countries follow civil law, and precedence has a much more limited role than in common law countries. So it actually matters that the statutes be written clearly.
I don't think that there are any others though.
Law is meant to be precise. If it's not, then ignorance of the law does become an excuse and law loses its moral authority.
Unfortunately the EU does seem rather keen on laws so vague that they're impossible to understand - it's rule by law, not rule of law.
As for your strawman that I somehow argued to abandon all law: I won't deal with that.
Only a few technical, minor points need to be spelled out in national regulations or laws.
Each country (or state, in the case of Germany I believe) will have their own privacy commissioner with substantial leeway. Now technically these differences won't be implemented as laws, but there will be substantial differences between eg the French and the UK privacy regulators.
The GDPR also allows for individual states to strengthen its provisions, eg for genetic data.
I think that's a good thing. So the law has to be interpreted by precedence set by the courts.
If the text of is too specific you could have the opposite effect of companies weaseling through.
It is not a tax. It's pretty clear that the EU expects companies to treat private user data with respect. If your company cannot operate without exploiting this info, than maybe the world is better off without it anyway.