> Yes but unfortunately courts are mostly reactive, not proactive

I think it’s always the case, no? Unless the unconstitutional law is approved, there is nothing to dispute in court.

In the Netherlands we have the “Eerste kamer” (first chamber, also called Senate) that is responsible for verifying that the proposed laws are in accordance with our “constitution”. They are elected of band with the normal government which should ensure that no single party is able to steamroll laws through both chambers.

In theory the "Bundespräsident" in Germany is supposed to only ratify laws that are in accordance with the constitution, but I don't think it happens that he refuses to do this.

Correct. Imagine the number of challenges in court based on mere rumor of a law.