Inefficient Politicians, vague Laws
Many Directives are purposely made so vague, that it is later left over to the judiciry to fill in the blanks, so to say. In terms of human rights, national high courts have often had a hard time figuring out exactly what the law means, and have had to ask the European Court for a decision to set the direction. Many have been on timing, how long may a person have to wait for a national ruling on extradiction, repatriation, or even just a simple ruling in a civil case. Such time limits should and must be decided by law, by the politicians, not by judges that are not elected and have no accountability for the average citizen of member countries.
You may say, but courts are not only in place to apply the law to contest cases an decide on the application of existing law. They are also generally in place to interpret the law in any cases of vagueness or disputed interpretations of the law. Yes, that is correct, but it is also clear that if the laws are too vague and disputed about the real mening of the content, then the laws need to be corrected and specified much more clearly. And that is the responsibility of elected officers that can be held responsible for their decisions by the electorate.
The EU has a huge problem with laws that are much too vague and are effectively just scaffolding that the courts have to fill in. It is amazing that the enourmous EU bureaucracy is working under vague rules that they have to seek case law to understand. Such should rarely be the case, and politicians must always be aware in order for them to react quickly to rectify the situation. Keeping in mimd that the EU is a fairly recent creation, there is no big volumes of case law like e.g. in the British or American systems where most vaguenesses are since decades or even centuries have been filled in by case law.