I live in Germany and take the train all the time. There were always kind of clusters of issues, but lately I haven't had many problems, especially not major, don't really remember what the last time was I got any compensation for over an hour delay. The last time was maybe two years ago.

I wonder sometimes how these things develop because if you're objectively pissed off that your train was delayed, I cannot imagine enjoying taking the plane, or even worse a car. Like I haven't had a plane take off on time in my life. I took only a few business trips with the car and was stuck in traffic every single time. So objectively despite experiencing issues with DB myself, it's a lot better than my experience with alternatives. Stuttgart - Leipzig has a direct connection, and in my experience the biggest reason for a delay is when you miss a connecting train. E.g. your train is 15 minutes late but you had only 10 minutes to change trains. So other than the train going out of service I honestly can't imagine what the issue would be. You sit for 4h, can work comfortably, it's quieter than anything else, you can have a coffee or a beer, a meal etc. etc. And then maybe you'll have a half hour delay, but you can get that with anything else also.