> Most of the whining I've heard about DB boils down to inconvenience in situations nobody could have predicted nor helped [..]

I agree with you that there’s a lot of complaining and it does get tiresome. The German train system is one of the most complex in the world and works closer to an interconnected spider web than the typical straight line systems in other countries.

However much of this has been predicted in the past. I think that’s why a lot of people are annoyed. Here are some sources if you’re interested to read more:

(2006) Audit critique regarding the bad state of DB funding after privatization: https://dserver.bundestag.de/btd/16/008/1600840.pdf

(2011) DB is not spending enough on the track network: https://taz.de/Investitionen-in-das-Schienennetz/%215117195/

(2014) State of German train bridges: https://www.zeit.de/mobilitaet/2014-09/deutsche-bahn-bruecke...