DBahn was privatized in a way that combines the worst of both worlds: private but 100% owned by the state. Opaque labyrinth of 600 subcompanies.
Also, some textbook examples of bad incentives. For example, repairing bridges is paid by DB. If a bridge is beyond repair, then the tax payer pays. Predictable result: doing hardly any maintenance until the bridge fails. (That example is by now fixed, but shows the clear lack of planning)
Finally, the system is just over capacity. Many more trains but same infrastructure as decades ago. If you got rid of half the schedule and used a swiss-like system of stopping several minutes at every station, the trains could be on time. But the trains already are overcrowded, so then what do you do with all the passengers?
Also, some textbook examples of bad incentives. For example, repairing bridges is paid by DB. If a bridge is beyond repair, then the tax payer pays. Predictable result: doing hardly any maintenance until the bridge fails. (That example is by now fixed, but shows the clear lack of planning)
Finally, the system is just over capacity. Many more trains but same infrastructure as decades ago. If you got rid of half the schedule and used a swiss-like system of stopping several minutes at every station, the trains could be on time. But the trains already are overcrowded, so then what do you do with all the passengers?