Just saying "It's unconstitutional" doesn't really cut it. It's a question for the courts to decide (based on the constitution).

A constitution is the basic big-picture law of the country. The court’s interpretation should be easy to guess. Otherwise, the people won’t feel like it is their document.

Rule of law is aided by laws that people know how to follow.

At least in America, a classic go to for Republican and democrats alike for opposing legislation is "that's unconstitutional!"

Sure, I’m from the US as well. In our case, I think this stems from multiple problems—the popular understanding of the constitution and the letter of the thing have diverged, and also the Supreme Court has gone in a third totally unrelated direction. So it becomes a convenient rhetorical meme. (IMO, we should the thing once a generation and have the populace re-ratify it with a high consensus, so we’re all on the same page).

I’m not sure if that’s the case in Germany though.

as the constitution doesn't have that high of a place in our identity it's more something for constitutional lawyers and higher courts. I think there's more tension between our constitutional law and that of the EU's law. for most people that's background noise I guess.

In this particular question there are also fundamental human rights that are part of the EU legislation where it is fully plausible that ECJ would render any law implementing the EU law. Like Ipred, where our politicians tried to pass laws following it but it got struck down again and again. No idea if they have given up yet.

They did already, multiple times now. Hence my original comment.