I think there are two main issues with trains in Germany. The first one is delays. It happens indeed more often than what I experienced with french trains, but I could handle this honestly. The second and bigger problem is that it seems like Deutsche Bahn never took their probable delays into account when planning your trip. How many times did I get a connection 15 min after my arrival? If you know your network is prone to delays, why do you keep putting travelers in this situation? Even worse, when your train is late and you miss your connection, there's not so much information about the available solutions. It always feels like it's a exceptional weird issue.