I think it varies. I suspect in most common cases the lack of enforcement results from the rest of society not having an appetite to punish it. No harm done, no need to punish.

I believe jaywalking (or crossing a red light as a pedestrian) is prohibited, but you would have to do it in front of a really motivated cop (or cause an accident) to actually get a ticket for it. It is common and no one really cares - but if you were to do it in front of children or a school you will probably get disapproving looks or a somewhat stern talking to from others around you.

I think the image of the "order-loving german" is a bit of a stereotype. Some people overdo it (Calling the police for noise harassment if you still mow your lawn at 20:01), but they are generally not popular with their neighbors (or the police...)

The population is very diverse about this I would say. Some people would stand at a red light as pedestrians until they starve to death while others don't give a fuck about anything.

IIRC there is actually a practice of nullifying laws that cannot be enforced (Vollzugsdefizit). One example I remember is that the enforcement of minor drug possession charges was declared unconstitutional because that law was only selectively enforced.