The TL;DR is: regional trains are usually on time, long-distance trains usually are not. If you need to travel between cities, plan with an hour buffer time. Basically, "show some adaptability".

The one good thing about frequent long-distance delays is that you might be lucky and catch an earlier delayed train and actually arrive a bit earlier than planned ;)

(also JFC, does the author like to whine about nothing - I'm travelling frequently with DB for about 25 years now, and while shit happens from time time, most of it is merely a slight inconvenience).

Plan with a ~40% of travel time buffer if you ought be there, and travel the day before if you must be there.

I travel from Basel to Hannover and back every two weeks on DB. Trains south are almost always late, trains north usually late. Frequently the train is already late in Hannover having come from Hamburg. The worst was when I was kicked out in Frankfurt and had to stay in a hotel. The delays were so bad there were no more trains left that could connect me to the last train out of Basel.

Things have been getting better for the past couple of months I think though.